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	$61.45	7.445%	$66.025	$66.03	$66.05	$66.00
Purchase #2	$148.74	5.174%	$156.4358	$156.44	$156.45	$156.40
Purchase #3	$85.94	10.372%	$94.8537	$94.85	$94.85	$94.90
Purchase #4	$52.46	5.572%	$55.3831	$55.38	$55.40	$55.40
Purchase #5	$191.98	13.872%	$218.6115	$218.61	$218.60	$218.60
Purchase #6	$74.98	13.538%	$85.1308	$85.13	$85.15	$85.10
Purchase #7	$114.67	9.501%	$125.5648	$125.56	$125.55	$125.60
7 purchase totals =	$730.22		$802.0047	$802.00	$802.05	$802.00