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	$54.60	13.842%	$62.1577	$62.16	$62.15	$62.20
Purchase #2	$109.79	10.569%	$121.3937	$121.39	$121.40	$121.40
Purchase #3	$187.31	4.414%	$195.5779	$195.58	$195.60	$195.60
Purchase #4	$61.48	9.703%	$67.4454	$67.45	$67.45	$67.40
Purchase #5	$224.56	6.263%	$238.6242	$238.62	$238.60	$238.60
Purchase #6	$172.65	9.385%	$188.8532	$188.85	$188.85	$188.90
Purchase #7	$54.41	3.240%	$56.1729	$56.17	$56.15	$56.20
7 purchase totals =	$864.80		$930.2250	$930.22	$930.20	$930.30