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	$91.42	6.679%	$97.5259	$97.53	$97.55	$97.50
Purchase #2	$40.61	12.842%	$45.8251	$45.83	$45.85	$45.80
Purchase #3	$137.66	9.408%	$150.6111	$150.61	$150.60	$150.60
Purchase #4	$238.72	12.481%	$268.5146	$268.51	$268.50	$268.50
Purchase #5	$120.38	10.167%	$132.619	$132.62	$132.60	$132.60
Purchase #6	$115.79	9.791%	$127.127	$127.13	$127.15	$127.10
Purchase #7	$200.40	7.152%	$214.7326	$214.73	$214.75	$214.70
7 purchase totals =	$944.98		$1,036.9553	$1,036.96	$1,037.00	$1,036.80