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	$167.50	9.325%	$183.1194	$183.12	$183.10	$183.10
Purchase #2	$34.66	3.361%	$35.8249	$35.82	$35.80	$35.80
Purchase #3	$176.84	6.632%	$188.568	$188.57	$188.55	$188.60
Purchase #4	$116.69	11.627%	$130.2575	$130.26	$130.25	$130.30
Purchase #5	$185.68	12.683%	$209.2298	$209.23	$209.25	$209.20
Purchase #6	$207.83	4.307%	$216.7812	$216.78	$216.80	$216.80
Purchase #7	$48.28	9.864%	$53.0423	$53.04	$53.05	$53.00
7 purchase totals =	$937.48		$1,016.8231	$1,016.82	$1,016.80	$1,016.80