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	$139.56	7.719%	$150.3326	$150.33	$150.35	$150.30
Purchase #2	$136.61	6.575%	$145.5921	$145.59	$145.60	$145.60
Purchase #3	$69.57	13.757%	$79.1407	$79.14	$79.15	$79.10
Purchase #4	$119.89	10.123%	$132.0265	$132.03	$132.05	$132.00
Purchase #5	$182.54	3.401%	$188.7482	$188.75	$188.75	$188.70
Purchase #6	$132.38	8.196%	$143.2299	$143.23	$143.25	$143.20
Purchase #7	$99.86	3.181%	$103.0365	$103.04	$103.05	$103.00
7 purchase totals =	$880.41		$942.1065	$942.11	$942.20	$941.90