Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.27	13.247%	$191.6932	$191.69	$191.70	$191.70
Purchase #2	$117.36	11.817%	$131.2284	$131.23	$131.25	$131.20
Purchase #3	$198.28	11.771%	$221.6195	$221.62	$221.60	$221.60
Purchase #4	$147.56	3.220%	$152.3114	$152.31	$152.30	$152.30
Purchase #5	$221.65	5.759%	$234.4148	$234.41	$234.40	$234.40
Purchase #6	$106.47	5.590%	$112.4217	$112.42	$112.40	$112.40
Purchase #7	$113.25	13.433%	$128.4629	$128.46	$128.45	$128.50
7 purchase totals =	$1,073.84		$1,172.1519	$1,172.14	$1,172.10	$1,172.10