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	$223.47	10.538%	$247.0193	$247.02	$247.00	$247.00
Purchase #2	$235.51	3.744%	$244.3275	$244.33	$244.35	$244.30
Purchase #3	$65.89	9.671%	$72.2622	$72.26	$72.25	$72.30
Purchase #4	$57.39	3.320%	$59.2953	$59.30	$59.30	$59.30
Purchase #5	$99.72	11.432%	$111.12	$111.12	$111.10	$111.10
Purchase #6	$36.87	5.862%	$39.0313	$39.03	$39.05	$39.00
Purchase #7	$58.88	6.283%	$62.5794	$62.58	$62.60	$62.60
7 purchase totals =	$777.73		$835.6350	$835.64	$835.65	$835.60