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	$55.31	13.633%	$62.8504	$62.85	$62.85	$62.90
Purchase #2	$128.63	10.676%	$142.3625	$142.36	$142.35	$142.40
Purchase #3	$54.61	9.392%	$59.739	$59.74	$59.75	$59.70
Purchase #4	$140.81	13.776%	$160.208	$160.21	$160.20	$160.20
Purchase #5	$239.54	10.504%	$264.7013	$264.70	$264.70	$264.70
Purchase #6	$159.89	7.170%	$171.3541	$171.35	$171.35	$171.40
Purchase #7	$144.43	5.219%	$151.9678	$151.97	$151.95	$152.00
7 purchase totals =	$923.22		$1,013.1831	$1,013.18	$1,013.15	$1,013.30