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	$38.64	7.453%	$41.5198	$41.52	$41.50	$41.50
Purchase #2	$248.34	13.269%	$281.2922	$281.29	$281.30	$281.30
Purchase #3	$138.82	13.656%	$157.7773	$157.78	$157.80	$157.80
Purchase #4	$165.35	4.462%	$172.7279	$172.73	$172.75	$172.70
Purchase #5	$74.27	11.121%	$82.5296	$82.53	$82.55	$82.50
Purchase #6	$224.98	6.700%	$240.0537	$240.05	$240.05	$240.10
Purchase #7	$85.93	6.730%	$91.7131	$91.71	$91.70	$91.70
7 purchase totals =	$976.33		$1,067.6136	$1,067.61	$1,067.65	$1,067.60