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	$82.50	11.656%	$92.1162	$92.12	$92.10	$92.10
Purchase #2	$33.82	12.122%	$37.9197	$37.92	$37.90	$37.90
Purchase #3	$36.29	7.427%	$38.9853	$38.99	$39.00	$39.00
Purchase #4	$33.27	3.544%	$34.4491	$34.45	$34.45	$34.40
Purchase #5	$62.97	13.442%	$71.4344	$71.43	$71.45	$71.40
Purchase #6	$222.88	13.583%	$253.1538	$253.15	$253.15	$253.20
Purchase #7	$93.61	10.348%	$103.2968	$103.30	$103.30	$103.30
7 purchase totals =	$565.34		$631.3553	$631.36	$631.35	$631.30