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	$85.32	10.255%	$94.0696	$94.07	$94.05	$94.10
Purchase #2	$234.96	12.205%	$263.6369	$263.64	$263.65	$263.60
Purchase #3	$225.83	7.800%	$243.4447	$243.44	$243.45	$243.40
Purchase #4	$68.90	12.873%	$77.7695	$77.77	$77.75	$77.80
Purchase #5	$95.81	10.169%	$105.5529	$105.55	$105.55	$105.60
Purchase #6	$201.81	7.211%	$216.3625	$216.36	$216.35	$216.40
Purchase #7	$93.70	6.841%	$100.11	$100.11	$100.10	$100.10
7 purchase totals =	$1,006.33		$1,100.9461	$1,100.94	$1,100.90	$1,101.00