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	$62.27	10.325%	$68.6994	$68.70	$68.70	$68.70
Purchase #2	$152.60	8.348%	$165.339	$165.34	$165.35	$165.30
Purchase #3	$158.59	4.666%	$165.9898	$165.99	$166.00	$166.00
Purchase #4	$73.76	6.267%	$78.3825	$78.38	$78.40	$78.40
Purchase #5	$145.46	4.822%	$152.4741	$152.47	$152.45	$152.50
Purchase #6	$171.52	7.446%	$184.2914	$184.29	$184.30	$184.30
Purchase #7	$172.75	11.128%	$191.9736	$191.97	$191.95	$192.00
7 purchase totals =	$936.95		$1,007.1498	$1,007.14	$1,007.15	$1,007.20