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	$239.58	6.336%	$254.7598	$254.76	$254.75	$254.80
Purchase #2	$149.77	11.409%	$166.8573	$166.86	$166.85	$166.90
Purchase #3	$107.70	3.250%	$111.2003	$111.20	$111.20	$111.20
Purchase #4	$7.33	7.119%	$7.8518	$7.85	$7.85	$7.90
Purchase #5	$217.99	3.447%	$225.5041	$225.50	$225.50	$225.50
Purchase #6	$129.48	12.169%	$145.2364	$145.24	$145.25	$145.20
Purchase #7	$89.85	11.365%	$100.0615	$100.06	$100.05	$100.10
7 purchase totals =	$941.70		$1,011.4712	$1,011.47	$1,011.45	$1,011.60