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	$51.40	3.325%	$53.1091	$53.11	$53.10	$53.10
Purchase #2	$76.58	5.378%	$80.6985	$80.70	$80.70	$80.70
Purchase #3	$54.27	6.457%	$57.7742	$57.77	$57.75	$57.80
Purchase #4	$166.43	12.460%	$187.1672	$187.17	$187.15	$187.20
Purchase #5	$72.30	11.130%	$80.347	$80.35	$80.35	$80.30
Purchase #6	$74.60	10.313%	$82.2935	$82.29	$82.30	$82.30
Purchase #7	$28.96	11.541%	$32.3023	$32.30	$32.30	$32.30
7 purchase totals =	$524.54		$573.6918	$573.69	$573.65	$573.70