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	$181.75	7.742%	$195.8211	$195.82	$195.80	$195.80
Purchase #2	$111.65	10.442%	$123.3085	$123.31	$123.30	$123.30
Purchase #3	$81.45	9.242%	$88.9776	$88.98	$89.00	$89.00
Purchase #4	$74.84	8.832%	$81.4499	$81.45	$81.45	$81.40
Purchase #5	$219.73	12.245%	$246.6359	$246.64	$246.65	$246.60
Purchase #6	$147.55	7.498%	$158.6133	$158.61	$158.60	$158.60
Purchase #7	$161.33	13.184%	$182.5997	$182.60	$182.60	$182.60
7 purchase totals =	$978.30		$1,077.4060	$1,077.41	$1,077.40	$1,077.30