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	$217.84	4.590%	$227.8389	$227.84	$227.85	$227.80
Purchase #2	$96.45	9.212%	$105.335	$105.34	$105.35	$105.30
Purchase #3	$76.40	3.374%	$78.9777	$78.98	$79.00	$79.00
Purchase #4	$209.82	13.243%	$237.6065	$237.61	$237.60	$237.60
Purchase #5	$174.33	9.164%	$190.3056	$190.31	$190.30	$190.30
Purchase #6	$10.45	10.548%	$11.5523	$11.55	$11.55	$11.60
Purchase #7	$158.92	12.709%	$179.1171	$179.12	$179.10	$179.10
7 purchase totals =	$944.21		$1,030.7331	$1,030.75	$1,030.75	$1,030.70