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	$41.57	4.118%	$43.2819	$43.28	$43.30	$43.30
Purchase #2	$133.90	5.864%	$141.7519	$141.75	$141.75	$141.80
Purchase #3	$17.96	7.715%	$19.3456	$19.35	$19.35	$19.30
Purchase #4	$140.57	11.208%	$156.3251	$156.33	$156.35	$156.30
Purchase #5	$51.59	13.173%	$58.386	$58.39	$58.40	$58.40
Purchase #6	$92.89	11.258%	$103.3476	$103.35	$103.35	$103.30
Purchase #7	$135.50	11.484%	$151.0608	$151.06	$151.05	$151.10
7 purchase totals =	$613.98		$673.4989	$673.51	$673.55	$673.50