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	$218.50	6.414%	$232.5146	$232.51	$232.50	$232.50
Purchase #2	$214.33	5.220%	$225.518	$225.52	$225.50	$225.50
Purchase #3	$31.82	6.478%	$33.8813	$33.88	$33.90	$33.90
Purchase #4	$149.50	10.574%	$165.3081	$165.31	$165.30	$165.30
Purchase #5	$96.68	3.395%	$99.9623	$99.96	$99.95	$100.00
Purchase #6	$104.43	9.625%	$114.4814	$114.48	$114.50	$114.50
Purchase #7	$94.57	11.765%	$105.6962	$105.70	$105.70	$105.70
7 purchase totals =	$909.83		$977.3619	$977.36	$977.35	$977.40