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	$133.94	5.698%	$141.5719	$141.57	$141.55	$141.60
Purchase #2	$91.76	8.601%	$99.6523	$99.65	$99.65	$99.70
Purchase #3	$100.90	4.313%	$105.2518	$105.25	$105.25	$105.30
Purchase #4	$66.84	8.283%	$72.3764	$72.38	$72.40	$72.40
Purchase #5	$62.35	12.469%	$70.1244	$70.12	$70.10	$70.10
Purchase #6	$145.28	9.813%	$159.5363	$159.54	$159.55	$159.50
Purchase #7	$86.43	10.598%	$95.5899	$95.59	$95.60	$95.60
7 purchase totals =	$687.50		$744.1030	$744.10	$744.10	$744.20