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	$72.92	13.575%	$82.8189	$82.82	$82.80	$82.80
Purchase #2	$79.99	11.618%	$89.2832	$89.28	$89.30	$89.30
Purchase #3	$83.48	5.616%	$88.1682	$88.17	$88.15	$88.20
Purchase #4	$223.98	12.570%	$252.1343	$252.13	$252.15	$252.10
Purchase #5	$53.97	10.800%	$59.7988	$59.80	$59.80	$59.80
Purchase #6	$185.38	6.642%	$197.6929	$197.69	$197.70	$197.70
Purchase #7	$82.73	7.606%	$89.0224	$89.02	$89.00	$89.00
7 purchase totals =	$782.45		$858.9187	$858.91	$858.90	$858.90