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	$53.84	3.520%	$55.7352	$55.74	$55.75	$55.70
Purchase #2	$205.96	11.826%	$230.3168	$230.32	$230.30	$230.30
Purchase #3	$51.72	6.561%	$55.1133	$55.11	$55.10	$55.10
Purchase #4	$235.81	8.688%	$256.2972	$256.30	$256.30	$256.30
Purchase #5	$213.69	10.505%	$236.1381	$236.14	$236.15	$236.10
Purchase #6	$200.59	4.196%	$209.0068	$209.01	$209.00	$209.00
Purchase #7	$58.96	5.805%	$62.3826	$62.38	$62.40	$62.40
7 purchase totals =	$1,020.57		$1,104.9900	$1,105.00	$1,105.00	$1,104.90