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	$134.81	12.107%	$151.1314	$151.13	$151.15	$151.10
Purchase #2	$39.47	7.765%	$42.5348	$42.53	$42.55	$42.50
Purchase #3	$244.84	7.463%	$263.1124	$263.11	$263.10	$263.10
Purchase #4	$223.36	11.795%	$249.7053	$249.71	$249.70	$249.70
Purchase #5	$173.94	8.707%	$189.085	$189.09	$189.10	$189.10
Purchase #6	$225.46	8.215%	$243.9815	$243.98	$244.00	$244.00
Purchase #7	$71.39	9.668%	$78.292	$78.29	$78.30	$78.30
7 purchase totals =	$1,113.27		$1,217.8424	$1,217.84	$1,217.90	$1,217.80