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	$109.25	4.245%	$113.8877	$113.89	$113.90	$113.90
Purchase #2	$50.62	6.590%	$53.9559	$53.96	$53.95	$54.00
Purchase #3	$192.61	3.168%	$198.7119	$198.71	$198.70	$198.70
Purchase #4	$132.86	4.873%	$139.3343	$139.33	$139.35	$139.30
Purchase #5	$91.31	3.155%	$94.1908	$94.19	$94.20	$94.20
Purchase #6	$61.93	6.300%	$65.8316	$65.83	$65.85	$65.80
Purchase #7	$91.81	13.483%	$104.1887	$104.19	$104.20	$104.20
7 purchase totals =	$730.39		$770.1009	$770.10	$770.15	$770.10