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	$231.41	6.751%	$247.0325	$247.03	$247.05	$247.00
Purchase #2	$74.96	6.824%	$80.0753	$80.08	$80.10	$80.10
Purchase #3	$106.97	3.800%	$111.0349	$111.03	$111.05	$111.00
Purchase #4	$223.26	7.516%	$240.0402	$240.04	$240.05	$240.00
Purchase #5	$88.88	3.147%	$91.6771	$91.68	$91.70	$91.70
Purchase #6	$166.69	4.315%	$173.8827	$173.88	$173.90	$173.90
Purchase #7	$148.83	11.256%	$165.5823	$165.58	$165.60	$165.60
7 purchase totals =	$1,041.00		$1,109.3250	$1,109.32	$1,109.45	$1,109.30