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	$68.38	4.651%	$71.5604	$71.56	$71.55	$71.60
Purchase #2	$10.27	5.459%	$10.8306	$10.83	$10.85	$10.80
Purchase #3	$171.96	4.104%	$179.0172	$179.02	$179.00	$179.00
Purchase #4	$88.77	4.642%	$92.8907	$92.89	$92.90	$92.90
Purchase #5	$181.65	3.547%	$188.0931	$188.09	$188.10	$188.10
Purchase #6	$35.41	13.792%	$40.2937	$40.29	$40.30	$40.30
Purchase #7	$141.67	5.161%	$148.9816	$148.98	$149.00	$149.00
7 purchase totals =	$698.11		$731.6673	$731.66	$731.70	$731.70