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	$118.91	10.513%	$131.411	$131.41	$131.40	$131.40
Purchase #2	$69.55	3.815%	$72.2033	$72.20	$72.20	$72.20
Purchase #3	$95.35	11.460%	$106.2771	$106.28	$106.30	$106.30
Purchase #4	$122.55	11.842%	$137.0624	$137.06	$137.05	$137.10
Purchase #5	$117.49	5.245%	$123.6524	$123.65	$123.65	$123.70
Purchase #6	$157.64	13.579%	$179.0459	$179.05	$179.05	$179.00
Purchase #7	$153.72	8.751%	$167.172	$167.17	$167.15	$167.20
7 purchase totals =	$835.21		$916.8241	$916.82	$916.80	$916.90