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	$50.77	7.814%	$54.7372	$54.74	$54.75	$54.70
Purchase #2	$134.56	12.541%	$151.4352	$151.44	$151.45	$151.40
Purchase #3	$151.51	5.127%	$159.2779	$159.28	$159.30	$159.30
Purchase #4	$236.89	11.694%	$264.5919	$264.59	$264.60	$264.60
Purchase #5	$174.50	12.537%	$196.3771	$196.38	$196.40	$196.40
Purchase #6	$175.85	8.466%	$190.7375	$190.74	$190.75	$190.70
Purchase #7	$155.32	8.790%	$168.9726	$168.97	$168.95	$169.00
7 purchase totals =	$1,079.40		$1,186.1294	$1,186.14	$1,186.20	$1,186.10