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	$228.29	8.388%	$247.439	$247.44	$247.45	$247.40
Purchase #2	$98.38	11.644%	$109.8354	$109.84	$109.85	$109.80
Purchase #3	$248.62	7.852%	$268.1416	$268.14	$268.15	$268.10
Purchase #4	$117.78	6.470%	$125.4004	$125.40	$125.40	$125.40
Purchase #5	$241.33	5.872%	$255.5009	$255.50	$255.50	$255.50
Purchase #6	$58.33	12.544%	$65.6469	$65.65	$65.65	$65.60
Purchase #7	$35.46	13.622%	$40.2904	$40.29	$40.30	$40.30
7 purchase totals =	$1,028.19		$1,112.2546	$1,112.26	$1,112.30	$1,112.10