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	$66.72	8.160%	$72.1644	$72.16	$72.15	$72.20
Purchase #2	$226.31	9.642%	$248.1308	$248.13	$248.15	$248.10
Purchase #3	$153.52	11.459%	$171.1119	$171.11	$171.10	$171.10
Purchase #4	$234.68	12.629%	$264.3177	$264.32	$264.30	$264.30
Purchase #5	$94.40	8.762%	$102.6713	$102.67	$102.65	$102.70
Purchase #6	$195.27	12.545%	$219.7666	$219.77	$219.75	$219.80
Purchase #7	$71.32	9.610%	$78.1739	$78.17	$78.15	$78.20
7 purchase totals =	$1,042.22		$1,156.3366	$1,156.33	$1,156.25	$1,156.40