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	$95.72	4.354%	$99.8876	$99.89	$99.90	$99.90
Purchase #2	$79.95	10.140%	$88.0569	$88.06	$88.05	$88.10
Purchase #3	$219.52	8.760%	$238.75	$238.75	$238.75	$238.80
Purchase #4	$212.28	11.141%	$235.9301	$235.93	$235.95	$235.90
Purchase #5	$35.26	4.340%	$36.7903	$36.79	$36.80	$36.80
Purchase #6	$230.92	3.340%	$238.6327	$238.63	$238.65	$238.60
Purchase #7	$56.71	4.855%	$59.4633	$59.46	$59.45	$59.50
7 purchase totals =	$930.36		$997.5109	$997.51	$997.55	$997.60