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	$29.25	7.145%	$31.3399	$31.34	$31.35	$31.30
Purchase #2	$244.32	5.676%	$258.1876	$258.19	$258.20	$258.20
Purchase #3	$198.27	6.142%	$210.4477	$210.45	$210.45	$210.40
Purchase #4	$65.95	6.413%	$70.1794	$70.18	$70.20	$70.20
Purchase #5	$204.56	5.622%	$216.0604	$216.06	$216.05	$216.10
Purchase #6	$83.72	6.605%	$89.2497	$89.25	$89.25	$89.20
Purchase #7	$209.47	13.858%	$238.4984	$238.50	$238.50	$238.50
7 purchase totals =	$1,035.54		$1,113.9631	$1,113.97	$1,114.00	$1,113.90