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	$74.78	9.703%	$82.0359	$82.04	$82.05	$82.00
Purchase #2	$216.75	5.519%	$228.7124	$228.71	$228.70	$228.70
Purchase #3	$221.31	6.816%	$236.3945	$236.39	$236.40	$236.40
Purchase #4	$185.30	7.850%	$199.8461	$199.85	$199.85	$199.80
Purchase #5	$96.65	4.761%	$101.2515	$101.25	$101.25	$101.30
Purchase #6	$92.45	9.735%	$101.45	$101.45	$101.45	$101.50
Purchase #7	$237.52	5.518%	$250.6264	$250.63	$250.65	$250.60
7 purchase totals =	$1,124.76		$1,200.3168	$1,200.32	$1,200.35	$1,200.30