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	$137.77	10.693%	$152.5017	$152.50	$152.50	$152.50
Purchase #2	$9.25	11.440%	$10.3082	$10.31	$10.30	$10.30
Purchase #3	$165.68	5.109%	$174.1446	$174.14	$174.15	$174.10
Purchase #4	$25.26	12.207%	$28.3435	$28.34	$28.35	$28.30
Purchase #5	$232.91	8.812%	$253.434	$253.43	$253.45	$253.40
Purchase #6	$63.46	12.629%	$71.4744	$71.47	$71.45	$71.50
Purchase #7	$151.87	12.597%	$171.0011	$171.00	$171.00	$171.00
7 purchase totals =	$786.20		$861.2075	$861.19	$861.20	$861.10