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	$78.61	5.288%	$82.7669	$82.77	$82.75	$82.80
Purchase #2	$247.29	5.149%	$260.023	$260.02	$260.00	$260.00
Purchase #3	$166.53	7.204%	$178.5268	$178.53	$178.55	$178.50
Purchase #4	$161.43	3.399%	$166.917	$166.92	$166.90	$166.90
Purchase #5	$81.73	13.635%	$92.8739	$92.87	$92.85	$92.90
Purchase #6	$239.89	10.117%	$264.1597	$264.16	$264.15	$264.20
Purchase #7	$223.81	6.723%	$238.8567	$238.86	$238.85	$238.90
7 purchase totals =	$1,199.29		$1,284.1240	$1,284.13	$1,284.05	$1,284.20