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	$81.79	13.747%	$93.0337	$93.03	$93.05	$93.00
Purchase #2	$83.57	9.179%	$91.2409	$91.24	$91.25	$91.20
Purchase #3	$125.64	3.533%	$130.0789	$130.08	$130.10	$130.10
Purchase #4	$243.48	11.458%	$271.3779	$271.38	$271.40	$271.40
Purchase #5	$161.77	6.861%	$172.869	$172.87	$172.85	$172.90
Purchase #6	$186.32	12.422%	$209.4647	$209.46	$209.45	$209.50
Purchase #7	$43.66	4.837%	$45.7718	$45.77	$45.75	$45.80
7 purchase totals =	$926.23		$1,013.8369	$1,013.83	$1,013.85	$1,013.90