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	$125.38	13.377%	$142.1521	$142.15	$142.15	$142.20
Purchase #2	$220.26	11.487%	$245.5613	$245.56	$245.55	$245.60
Purchase #3	$152.61	12.587%	$171.819	$171.82	$171.80	$171.80
Purchase #4	$122.99	5.734%	$130.0422	$130.04	$130.05	$130.00
Purchase #5	$238.25	11.237%	$265.0222	$265.02	$265.00	$265.00
Purchase #6	$130.71	5.498%	$137.8964	$137.90	$137.90	$137.90
Purchase #7	$47.47	12.499%	$53.4033	$53.40	$53.40	$53.40
7 purchase totals =	$1,037.67		$1,145.8965	$1,145.89	$1,145.85	$1,145.90