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	$166.47	11.153%	$185.0364	$185.04	$185.05	$185.00
Purchase #2	$190.67	9.214%	$208.2383	$208.24	$208.25	$208.20
Purchase #3	$209.30	9.716%	$229.6356	$229.64	$229.65	$229.60
Purchase #4	$136.57	11.634%	$152.4586	$152.46	$152.45	$152.50
Purchase #5	$130.30	6.865%	$139.2451	$139.25	$139.25	$139.20
Purchase #6	$210.80	9.216%	$230.2273	$230.23	$230.25	$230.20
Purchase #7	$198.38	12.142%	$222.4673	$222.47	$222.45	$222.50
7 purchase totals =	$1,242.49		$1,367.3086	$1,367.33	$1,367.35	$1,367.20