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	$74.86	5.857%	$79.2446	$79.24	$79.25	$79.20
Purchase #2	$95.66	4.860%	$100.3091	$100.31	$100.30	$100.30
Purchase #3	$246.74	11.593%	$275.3446	$275.34	$275.35	$275.30
Purchase #4	$131.85	6.633%	$140.5956	$140.60	$140.60	$140.60
Purchase #5	$112.70	12.812%	$127.1391	$127.14	$127.15	$127.10
Purchase #6	$115.57	7.474%	$124.2077	$124.21	$124.20	$124.20
Purchase #7	$155.73	10.866%	$172.6516	$172.65	$172.65	$172.70
7 purchase totals =	$933.11		$1,019.4923	$1,019.49	$1,019.50	$1,019.40