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	$89.76	3.592%	$92.9842	$92.98	$93.00	$93.00
Purchase #2	$205.96	12.146%	$230.9759	$230.98	$231.00	$231.00
Purchase #3	$243.38	8.300%	$263.5805	$263.58	$263.60	$263.60
Purchase #4	$144.94	5.386%	$152.7465	$152.75	$152.75	$152.70
Purchase #5	$162.27	4.436%	$169.4683	$169.47	$169.45	$169.50
Purchase #6	$162.70	11.106%	$180.7695	$180.77	$180.75	$180.80
Purchase #7	$85.30	4.118%	$88.8127	$88.81	$88.80	$88.80
7 purchase totals =	$1,094.31		$1,179.3376	$1,179.34	$1,179.35	$1,179.40