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	$129.80	8.724%	$141.1238	$141.12	$141.10	$141.10
Purchase #2	$51.61	6.801%	$55.12	$55.12	$55.10	$55.10
Purchase #3	$146.85	5.825%	$155.404	$155.40	$155.40	$155.40
Purchase #4	$74.81	10.306%	$82.5199	$82.52	$82.50	$82.50
Purchase #5	$109.94	6.236%	$116.7959	$116.80	$116.80	$116.80
Purchase #6	$243.26	5.345%	$256.2622	$256.26	$256.25	$256.30
Purchase #7	$156.38	6.515%	$166.5682	$166.57	$166.55	$166.60
7 purchase totals =	$912.65		$973.7940	$973.79	$973.70	$973.80