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	$224.43	9.837%	$246.5072	$246.51	$246.50	$246.50
Purchase #2	$130.77	11.695%	$146.0636	$146.06	$146.05	$146.10
Purchase #3	$50.82	11.687%	$56.7593	$56.76	$56.75	$56.80
Purchase #4	$148.66	13.224%	$168.3188	$168.32	$168.30	$168.30
Purchase #5	$219.82	13.764%	$250.076	$250.08	$250.10	$250.10
Purchase #6	$41.37	3.162%	$42.6781	$42.68	$42.70	$42.70
Purchase #7	$195.73	5.288%	$206.0802	$206.08	$206.10	$206.10
7 purchase totals =	$1,011.60		$1,116.4832	$1,116.49	$1,116.50	$1,116.60