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	$143.82	6.618%	$153.338	$153.34	$153.35	$153.30
Purchase #2	$172.33	13.834%	$196.1701	$196.17	$196.15	$196.20
Purchase #3	$73.40	6.546%	$78.2048	$78.20	$78.20	$78.20
Purchase #4	$210.52	4.709%	$220.4334	$220.43	$220.45	$220.40
Purchase #5	$127.83	4.112%	$133.0864	$133.09	$133.10	$133.10
Purchase #6	$113.93	10.405%	$125.7844	$125.78	$125.80	$125.80
Purchase #7	$222.67	9.669%	$244.2	$244.20	$244.20	$244.20
7 purchase totals =	$1,064.50		$1,151.2171	$1,151.21	$1,151.25	$1,151.20