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	$145.83	4.616%	$152.5615	$152.56	$152.55	$152.60
Purchase #2	$221.77	3.434%	$229.3856	$229.39	$229.40	$229.40
Purchase #3	$153.79	9.331%	$168.1401	$168.14	$168.15	$168.10
Purchase #4	$245.47	7.184%	$263.1046	$263.10	$263.10	$263.10
Purchase #5	$191.46	7.190%	$205.226	$205.23	$205.25	$205.20
Purchase #6	$34.37	3.657%	$35.6269	$35.63	$35.65	$35.60
Purchase #7	$227.73	8.186%	$246.372	$246.37	$246.35	$246.40
7 purchase totals =	$1,220.42		$1,300.4167	$1,300.42	$1,300.45	$1,300.40