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	$196.46	10.771%	$217.6207	$217.62	$217.60	$217.60
Purchase #2	$83.34	7.866%	$89.8955	$89.90	$89.90	$89.90
Purchase #3	$167.33	3.316%	$172.8787	$172.88	$172.90	$172.90
Purchase #4	$50.30	5.471%	$53.0519	$53.05	$53.05	$53.10
Purchase #5	$206.98	13.201%	$234.3034	$234.30	$234.30	$234.30
Purchase #6	$188.96	13.200%	$213.9027	$213.90	$213.90	$213.90
Purchase #7	$129.56	6.252%	$137.6601	$137.66	$137.65	$137.70
7 purchase totals =	$1,022.93		$1,119.3130	$1,119.31	$1,119.30	$1,119.40