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	$61.93	11.837%	$69.2607	$69.26	$69.25	$69.30
Purchase #2	$139.76	5.588%	$147.5698	$147.57	$147.55	$147.60
Purchase #3	$227.28	6.748%	$242.6169	$242.62	$242.60	$242.60
Purchase #4	$151.68	9.317%	$165.812	$165.81	$165.80	$165.80
Purchase #5	$56.39	5.190%	$59.3166	$59.32	$59.30	$59.30
Purchase #6	$96.75	11.538%	$107.913	$107.91	$107.90	$107.90
Purchase #7	$209.48	3.220%	$216.2253	$216.23	$216.25	$216.20
7 purchase totals =	$943.27		$1,008.7143	$1,008.72	$1,008.65	$1,008.70