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	$50.72	4.759%	$53.1338	$53.13	$53.15	$53.10
Purchase #2	$146.81	13.349%	$166.4077	$166.41	$166.40	$166.40
Purchase #3	$200.37	10.499%	$221.4068	$221.41	$221.40	$221.40
Purchase #4	$172.46	6.306%	$183.3353	$183.34	$183.35	$183.30
Purchase #5	$58.58	5.833%	$61.997	$62.00	$62.00	$62.00
Purchase #6	$165.56	3.606%	$171.5301	$171.53	$171.55	$171.50
Purchase #7	$229.78	3.783%	$238.4726	$238.47	$238.45	$238.50
7 purchase totals =	$1,024.28		$1,096.2833	$1,096.29	$1,096.30	$1,096.20