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	$43.62	13.693%	$49.5929	$49.59	$49.60	$49.60
Purchase #2	$82.82	8.354%	$89.7388	$89.74	$89.75	$89.70
Purchase #3	$212.61	5.158%	$223.5764	$223.58	$223.60	$223.60
Purchase #4	$126.33	8.750%	$137.3839	$137.38	$137.40	$137.40
Purchase #5	$92.77	11.813%	$103.7289	$103.73	$103.75	$103.70
Purchase #6	$85.42	3.835%	$88.6959	$88.70	$88.70	$88.70
Purchase #7	$236.98	6.137%	$251.5235	$251.52	$251.50	$251.50
7 purchase totals =	$880.55		$944.2403	$944.24	$944.30	$944.20