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	$210.27	7.443%	$225.9204	$225.92	$225.90	$225.90
Purchase #2	$242.52	3.808%	$251.7552	$251.76	$251.75	$251.80
Purchase #3	$48.38	12.571%	$54.4618	$54.46	$54.45	$54.50
Purchase #4	$249.62	6.324%	$265.406	$265.41	$265.40	$265.40
Purchase #5	$154.98	6.335%	$164.798	$164.80	$164.80	$164.80
Purchase #6	$76.41	7.668%	$82.2691	$82.27	$82.25	$82.30
Purchase #7	$198.76	11.625%	$221.8659	$221.87	$221.85	$221.90
7 purchase totals =	$1,180.94		$1,266.4764	$1,266.49	$1,266.40	$1,266.60