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	$230.32	5.696%	$243.439	$243.44	$243.45	$243.40
Purchase #2	$48.49	9.548%	$53.1198	$53.12	$53.10	$53.10
Purchase #3	$193.27	11.724%	$215.929	$215.93	$215.95	$215.90
Purchase #4	$93.86	6.460%	$99.9234	$99.92	$99.90	$99.90
Purchase #5	$203.83	5.554%	$215.1507	$215.15	$215.15	$215.20
Purchase #6	$170.83	12.211%	$191.6901	$191.69	$191.70	$191.70
Purchase #7	$70.95	13.150%	$80.2799	$80.28	$80.30	$80.30
7 purchase totals =	$1,011.55		$1,099.5319	$1,099.53	$1,099.55	$1,099.50