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	$68.76	7.820%	$74.137	$74.14	$74.15	$74.10
Purchase #2	$169.30	8.771%	$184.1493	$184.15	$184.15	$184.10
Purchase #3	$167.81	7.366%	$180.1709	$180.17	$180.15	$180.20
Purchase #4	$36.55	11.797%	$40.8618	$40.86	$40.85	$40.90
Purchase #5	$165.51	12.835%	$186.7532	$186.75	$186.75	$186.80
Purchase #6	$199.33	11.541%	$222.3347	$222.33	$222.35	$222.30
Purchase #7	$156.34	10.719%	$173.0981	$173.10	$173.10	$173.10
7 purchase totals =	$963.60		$1,061.5050	$1,061.50	$1,061.50	$1,061.50