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	$228.49	4.463%	$238.6875	$238.69	$238.70	$238.70
Purchase #2	$99.85	11.796%	$111.6283	$111.63	$111.65	$111.60
Purchase #3	$39.67	4.219%	$41.3437	$41.34	$41.35	$41.30
Purchase #4	$68.86	3.528%	$71.2894	$71.29	$71.30	$71.30
Purchase #5	$49.39	13.621%	$56.1174	$56.12	$56.10	$56.10
Purchase #6	$96.88	7.817%	$104.4531	$104.45	$104.45	$104.50
Purchase #7	$218.56	11.593%	$243.8977	$243.90	$243.90	$243.90
7 purchase totals =	$801.70		$867.4171	$867.42	$867.45	$867.40