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	$225.97	7.754%	$243.4917	$243.49	$243.50	$243.50
Purchase #2	$57.77	13.271%	$65.4367	$65.44	$65.45	$65.40
Purchase #3	$122.58	7.298%	$131.5259	$131.53	$131.55	$131.50
Purchase #4	$93.30	6.148%	$99.0361	$99.04	$99.05	$99.00
Purchase #5	$248.86	11.822%	$278.2802	$278.28	$278.30	$278.30
Purchase #6	$200.81	5.584%	$212.0232	$212.02	$212.00	$212.00
Purchase #7	$84.89	6.363%	$90.2916	$90.29	$90.30	$90.30
7 purchase totals =	$1,034.18		$1,120.0854	$1,120.09	$1,120.15	$1,120.00