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	$186.60	10.551%	$206.2882	$206.29	$206.30	$206.30
Purchase #2	$99.59	9.504%	$109.055	$109.06	$109.05	$109.10
Purchase #3	$61.89	9.550%	$67.8005	$67.80	$67.80	$67.80
Purchase #4	$190.78	11.300%	$212.3381	$212.34	$212.35	$212.30
Purchase #5	$220.57	10.766%	$244.3166	$244.32	$244.30	$244.30
Purchase #6	$239.56	10.413%	$264.5054	$264.51	$264.50	$264.50
Purchase #7	$31.91	8.612%	$34.6581	$34.66	$34.65	$34.70
7 purchase totals =	$1,030.90		$1,138.9619	$1,138.98	$1,138.95	$1,139.00