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	$54.82	8.425%	$59.4386	$59.44	$59.45	$59.40
Purchase #2	$140.86	8.215%	$152.4316	$152.43	$152.45	$152.40
Purchase #3	$238.61	13.621%	$271.1111	$271.11	$271.10	$271.10
Purchase #4	$192.80	11.657%	$215.2747	$215.27	$215.25	$215.30
Purchase #5	$166.42	3.715%	$172.6025	$172.60	$172.60	$172.60
Purchase #6	$117.59	6.430%	$125.151	$125.15	$125.15	$125.20
Purchase #7	$37.73	13.254%	$42.7307	$42.73	$42.75	$42.70
7 purchase totals =	$948.83		$1,038.7402	$1,038.73	$1,038.75	$1,038.70