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	$56.76	4.413%	$59.2648	$59.26	$59.25	$59.30
Purchase #2	$109.79	6.140%	$116.5311	$116.53	$116.55	$116.50
Purchase #3	$124.84	9.827%	$137.108	$137.11	$137.10	$137.10
Purchase #4	$96.75	3.107%	$99.756	$99.76	$99.75	$99.80
Purchase #5	$108.95	7.677%	$117.3141	$117.31	$117.30	$117.30
Purchase #6	$47.45	13.513%	$53.8619	$53.86	$53.85	$53.90
Purchase #7	$104.47	7.830%	$112.65	$112.65	$112.65	$112.70
7 purchase totals =	$649.01		$696.4859	$696.48	$696.45	$696.60