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	$219.53	13.496%	$249.1578	$249.16	$249.15	$249.20
Purchase #2	$38.89	13.366%	$44.088	$44.09	$44.10	$44.10
Purchase #3	$64.80	5.298%	$68.2331	$68.23	$68.25	$68.20
Purchase #4	$98.73	3.473%	$102.1589	$102.16	$102.15	$102.20
Purchase #5	$223.78	6.405%	$238.1131	$238.11	$238.10	$238.10
Purchase #6	$154.98	11.567%	$172.9065	$172.91	$172.90	$172.90
Purchase #7	$246.55	11.667%	$275.315	$275.32	$275.30	$275.30
7 purchase totals =	$1,047.26		$1,149.9724	$1,149.98	$1,149.95	$1,150.00