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	$91.84	5.454%	$96.849	$96.85	$96.85	$96.80
Purchase #2	$165.83	13.584%	$188.3563	$188.36	$188.35	$188.40
Purchase #3	$171.53	12.417%	$192.8289	$192.83	$192.85	$192.80
Purchase #4	$228.43	11.677%	$255.1038	$255.10	$255.10	$255.10
Purchase #5	$152.56	5.833%	$161.4588	$161.46	$161.45	$161.50
Purchase #6	$200.72	4.432%	$209.6159	$209.62	$209.60	$209.60
Purchase #7	$11.98	9.871%	$13.1625	$13.16	$13.15	$13.20
7 purchase totals =	$1,022.89		$1,117.3752	$1,117.38	$1,117.35	$1,117.40