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	$72.93	13.415%	$82.7136	$82.71	$82.70	$82.70
Purchase #2	$171.51	13.547%	$194.7445	$194.74	$194.75	$194.70
Purchase #3	$202.27	11.466%	$225.4623	$225.46	$225.45	$225.50
Purchase #4	$248.55	6.334%	$264.2932	$264.29	$264.30	$264.30
Purchase #5	$126.67	4.139%	$131.9129	$131.91	$131.90	$131.90
Purchase #6	$32.31	9.427%	$35.3559	$35.36	$35.35	$35.40
Purchase #7	$194.94	8.544%	$211.5957	$211.60	$211.60	$211.60
7 purchase totals =	$1,049.18		$1,146.0781	$1,146.07	$1,146.05	$1,146.10