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	$92.62	7.441%	$99.5119	$99.51	$99.50	$99.50
Purchase #2	$211.45	7.565%	$227.4462	$227.45	$227.45	$227.40
Purchase #3	$191.42	13.428%	$217.1239	$217.12	$217.10	$217.10
Purchase #4	$175.69	9.802%	$192.9111	$192.91	$192.90	$192.90
Purchase #5	$48.44	8.469%	$52.5424	$52.54	$52.55	$52.50
Purchase #6	$153.50	3.769%	$159.2854	$159.29	$159.30	$159.30
Purchase #7	$53.93	6.489%	$57.4295	$57.43	$57.45	$57.40
7 purchase totals =	$927.05		$1,006.2504	$1,006.25	$1,006.25	$1,006.10