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	$172.86	11.852%	$193.3474	$193.35	$193.35	$193.30
Purchase #2	$111.96	10.260%	$123.4471	$123.45	$123.45	$123.40
Purchase #3	$92.43	8.571%	$100.3522	$100.35	$100.35	$100.40
Purchase #4	$161.67	9.806%	$177.5234	$177.52	$177.50	$177.50
Purchase #5	$167.97	8.783%	$182.7228	$182.72	$182.70	$182.70
Purchase #6	$82.46	5.241%	$86.7817	$86.78	$86.80	$86.80
Purchase #7	$130.32	12.279%	$146.322	$146.32	$146.30	$146.30
7 purchase totals =	$919.67		$1,010.4966	$1,010.49	$1,010.45	$1,010.40