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	$210.37	8.138%	$227.4899	$227.49	$227.50	$227.50
Purchase #2	$184.45	6.560%	$196.5499	$196.55	$196.55	$196.50
Purchase #3	$145.42	8.450%	$157.708	$157.71	$157.70	$157.70
Purchase #4	$27.35	6.720%	$29.1879	$29.19	$29.20	$29.20
Purchase #5	$86.34	3.529%	$89.3869	$89.39	$89.40	$89.40
Purchase #6	$117.70	11.139%	$130.8106	$130.81	$130.80	$130.80
Purchase #7	$86.82	10.773%	$96.1731	$96.17	$96.15	$96.20
7 purchase totals =	$858.45		$927.3063	$927.31	$927.30	$927.30