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	$194.41	12.363%	$218.4449	$218.44	$218.45	$218.40
Purchase #2	$68.90	5.449%	$72.6544	$72.65	$72.65	$72.70
Purchase #3	$121.81	7.405%	$130.83	$130.83	$130.85	$130.80
Purchase #4	$136.82	6.253%	$145.3754	$145.38	$145.40	$145.40
Purchase #5	$47.34	12.860%	$53.4279	$53.43	$53.45	$53.40
Purchase #6	$145.81	4.671%	$152.6208	$152.62	$152.60	$152.60
Purchase #7	$242.66	10.516%	$268.1781	$268.18	$268.20	$268.20
7 purchase totals =	$957.75		$1,041.5315	$1,041.53	$1,041.60	$1,041.50