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	$226.33	3.350%	$233.9121	$233.91	$233.90	$233.90
Purchase #2	$224.30	10.383%	$247.5891	$247.59	$247.60	$247.60
Purchase #3	$230.95	5.296%	$243.1811	$243.18	$243.20	$243.20
Purchase #4	$147.42	7.398%	$158.3261	$158.33	$158.35	$158.30
Purchase #5	$75.31	7.281%	$80.7933	$80.79	$80.80	$80.80
Purchase #6	$79.71	8.490%	$86.4774	$86.48	$86.50	$86.50
Purchase #7	$59.63	10.574%	$65.9353	$65.94	$65.95	$65.90
7 purchase totals =	$1,043.65		$1,116.2144	$1,116.22	$1,116.30	$1,116.20