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	$191.81	12.371%	$215.5388	$215.54	$215.55	$215.50
Purchase #2	$225.67	12.647%	$254.2105	$254.21	$254.20	$254.20
Purchase #3	$38.54	6.124%	$40.9002	$40.90	$40.90	$40.90
Purchase #4	$209.54	7.457%	$225.1654	$225.17	$225.15	$225.20
Purchase #5	$136.98	10.364%	$151.1766	$151.18	$151.20	$151.20
Purchase #6	$67.53	4.636%	$70.6607	$70.66	$70.65	$70.70
Purchase #7	$209.53	7.687%	$225.6366	$225.64	$225.65	$225.60
7 purchase totals =	$1,079.60		$1,183.2888	$1,183.30	$1,183.30	$1,183.30