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	$157.40	5.112%	$165.4463	$165.45	$165.45	$165.40
Purchase #2	$172.29	7.834%	$185.7872	$185.79	$185.80	$185.80
Purchase #3	$124.29	12.544%	$139.8809	$139.88	$139.90	$139.90
Purchase #4	$215.35	3.748%	$223.4213	$223.42	$223.40	$223.40
Purchase #5	$73.86	11.476%	$82.3362	$82.34	$82.35	$82.30
Purchase #6	$24.39	6.683%	$26.02	$26.02	$26.00	$26.00
Purchase #7	$171.45	13.602%	$194.7706	$194.77	$194.75	$194.80
7 purchase totals =	$939.03		$1,017.6625	$1,017.67	$1,017.65	$1,017.60