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	$151.83	11.272%	$168.9443	$168.94	$168.95	$168.90
Purchase #2	$155.27	9.405%	$169.8731	$169.87	$169.85	$169.90
Purchase #3	$152.65	12.809%	$172.2029	$172.20	$172.20	$172.20
Purchase #4	$78.63	3.500%	$81.3821	$81.38	$81.40	$81.40
Purchase #5	$220.35	10.413%	$243.295	$243.30	$243.30	$243.30
Purchase #6	$197.35	11.501%	$220.0472	$220.05	$220.05	$220.00
Purchase #7	$92.39	10.850%	$102.4143	$102.41	$102.40	$102.40
7 purchase totals =	$1,048.47		$1,158.1589	$1,158.15	$1,158.15	$1,158.10