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	$227.33	8.739%	$247.1964	$247.20	$247.20	$247.20
Purchase #2	$33.81	12.730%	$38.114	$38.11	$38.10	$38.10
Purchase #3	$49.39	8.449%	$53.563	$53.56	$53.55	$53.60
Purchase #4	$214.58	11.119%	$238.4392	$238.44	$238.45	$238.40
Purchase #5	$195.69	13.527%	$222.161	$222.16	$222.15	$222.20
Purchase #6	$231.47	4.208%	$241.2103	$241.21	$241.20	$241.20
Purchase #7	$99.69	4.253%	$103.9298	$103.93	$103.95	$103.90
7 purchase totals =	$1,051.96		$1,144.6137	$1,144.61	$1,144.60	$1,144.60