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	$171.69	11.873%	$192.0748	$192.07	$192.05	$192.10
Purchase #2	$245.53	9.659%	$269.2457	$269.25	$269.25	$269.20
Purchase #3	$35.41	10.436%	$39.1054	$39.11	$39.10	$39.10
Purchase #4	$156.53	10.204%	$172.5023	$172.50	$172.50	$172.50
Purchase #5	$239.35	7.132%	$256.4204	$256.42	$256.40	$256.40
Purchase #6	$149.34	6.639%	$159.2547	$159.25	$159.25	$159.30
Purchase #7	$162.43	12.608%	$182.9092	$182.91	$182.90	$182.90
7 purchase totals =	$1,160.28		$1,271.5125	$1,271.51	$1,271.45	$1,271.50