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	$216.33	4.442%	$225.9394	$225.94	$225.95	$225.90
Purchase #2	$113.38	4.416%	$118.3869	$118.39	$118.40	$118.40
Purchase #3	$131.66	12.739%	$148.4322	$148.43	$148.45	$148.40
Purchase #4	$195.50	13.516%	$221.9238	$221.92	$221.90	$221.90
Purchase #5	$250.76	7.316%	$269.1056	$269.11	$269.10	$269.10
Purchase #6	$129.29	8.108%	$139.7728	$139.77	$139.75	$139.80
Purchase #7	$81.46	9.305%	$89.0399	$89.04	$89.05	$89.00
7 purchase totals =	$1,118.38		$1,212.6006	$1,212.60	$1,212.60	$1,212.50