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	$99.32	11.700%	$110.9404	$110.94	$110.95	$110.90
Purchase #2	$239.96	10.120%	$264.244	$264.24	$264.25	$264.20
Purchase #3	$178.34	10.238%	$196.5984	$196.60	$196.60	$196.60
Purchase #4	$151.90	3.503%	$157.2211	$157.22	$157.20	$157.20
Purchase #5	$241.74	6.592%	$257.6755	$257.68	$257.70	$257.70
Purchase #6	$243.38	8.691%	$264.5322	$264.53	$264.55	$264.50
Purchase #7	$56.71	4.152%	$59.0646	$59.06	$59.05	$59.10
7 purchase totals =	$1,211.35		$1,310.2762	$1,310.27	$1,310.30	$1,310.20