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	$150.90	10.231%	$166.3386	$166.34	$166.35	$166.30
Purchase #2	$163.61	11.167%	$181.8803	$181.88	$181.90	$181.90
Purchase #3	$245.69	3.657%	$254.6749	$254.67	$254.65	$254.70
Purchase #4	$91.25	8.684%	$99.1742	$99.17	$99.15	$99.20
Purchase #5	$171.59	4.426%	$179.1846	$179.18	$179.20	$179.20
Purchase #6	$196.88	7.720%	$212.0791	$212.08	$212.10	$212.10
Purchase #7	$161.42	10.834%	$178.9082	$178.91	$178.90	$178.90
7 purchase totals =	$1,181.34		$1,272.2399	$1,272.23	$1,272.25	$1,272.30