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	$169.47	3.498%	$175.3981	$175.40	$175.40	$175.40
Purchase #2	$60.88	8.768%	$66.218	$66.22	$66.20	$66.20
Purchase #3	$103.40	12.210%	$116.0251	$116.03	$116.05	$116.00
Purchase #4	$116.66	12.223%	$130.9194	$130.92	$130.90	$130.90
Purchase #5	$144.83	4.684%	$151.6138	$151.61	$151.60	$151.60
Purchase #6	$86.74	4.595%	$90.7257	$90.73	$90.75	$90.70
Purchase #7	$72.76	6.478%	$77.4734	$77.47	$77.45	$77.50
7 purchase totals =	$754.74		$808.3735	$808.38	$808.35	$808.30