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	$141.52	7.868%	$152.6548	$152.65	$152.65	$152.70
Purchase #2	$121.49	3.632%	$125.9025	$125.90	$125.90	$125.90
Purchase #3	$111.76	6.401%	$118.9138	$118.91	$118.90	$118.90
Purchase #4	$100.53	10.473%	$111.0585	$111.06	$111.05	$111.10
Purchase #5	$236.87	3.133%	$244.2911	$244.29	$244.30	$244.30
Purchase #6	$16.96	12.739%	$19.1205	$19.12	$19.10	$19.10
Purchase #7	$30.75	6.400%	$32.718	$32.72	$32.70	$32.70
7 purchase totals =	$759.88		$804.6592	$804.65	$804.60	$804.70