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	$155.50	8.128%	$168.139	$168.14	$168.15	$168.10
Purchase #2	$115.84	6.283%	$123.1182	$123.12	$123.10	$123.10
Purchase #3	$181.59	5.670%	$191.8862	$191.89	$191.90	$191.90
Purchase #4	$135.94	12.214%	$152.5437	$152.54	$152.55	$152.50
Purchase #5	$235.65	10.819%	$261.145	$261.15	$261.15	$261.10
Purchase #6	$234.53	8.389%	$254.2047	$254.20	$254.20	$254.20
Purchase #7	$196.88	13.355%	$223.1733	$223.17	$223.15	$223.20
7 purchase totals =	$1,255.93		$1,374.2101	$1,374.21	$1,374.20	$1,374.10