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	$129.60	3.485%	$134.1166	$134.12	$134.10	$134.10
Purchase #2	$197.83	4.364%	$206.4633	$206.46	$206.45	$206.50
Purchase #3	$76.40	11.656%	$85.3052	$85.31	$85.30	$85.30
Purchase #4	$39.90	6.211%	$42.3782	$42.38	$42.40	$42.40
Purchase #5	$23.53	3.501%	$24.3538	$24.35	$24.35	$24.40
Purchase #6	$30.89	3.235%	$31.8893	$31.89	$31.90	$31.90
Purchase #7	$61.36	10.158%	$67.5929	$67.59	$67.60	$67.60
7 purchase totals =	$559.51		$592.0993	$592.10	$592.10	$592.20