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	$200.28	5.659%	$211.6138	$211.61	$211.60	$211.60
Purchase #2	$61.31	11.284%	$68.2282	$68.23	$68.25	$68.20
Purchase #3	$172.85	6.634%	$184.3169	$184.32	$184.30	$184.30
Purchase #4	$232.53	4.873%	$243.8612	$243.86	$243.85	$243.90
Purchase #5	$243.52	11.505%	$271.537	$271.54	$271.55	$271.50
Purchase #6	$80.28	13.206%	$90.8818	$90.88	$90.90	$90.90
Purchase #7	$140.88	8.376%	$152.6801	$152.68	$152.70	$152.70
7 purchase totals =	$1,131.65		$1,223.1190	$1,223.12	$1,223.15	$1,223.10