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	$163.68	4.541%	$171.1127	$171.11	$171.10	$171.10
Purchase #2	$67.47	5.531%	$71.2018	$71.20	$71.20	$71.20
Purchase #3	$174.51	6.293%	$185.4919	$185.49	$185.50	$185.50
Purchase #4	$96.61	13.818%	$109.9596	$109.96	$109.95	$110.00
Purchase #5	$111.78	10.406%	$123.4118	$123.41	$123.40	$123.40
Purchase #6	$215.85	3.248%	$222.8608	$222.86	$222.85	$222.90
Purchase #7	$214.49	11.679%	$239.5403	$239.54	$239.55	$239.50
7 purchase totals =	$1,044.39		$1,123.5789	$1,123.57	$1,123.55	$1,123.60