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	$147.96	13.687%	$168.2113	$168.21	$168.20	$168.20
Purchase #2	$71.94	8.187%	$77.8297	$77.83	$77.85	$77.80
Purchase #3	$123.69	11.524%	$137.944	$137.94	$137.95	$137.90
Purchase #4	$25.77	6.237%	$27.3773	$27.38	$27.40	$27.40
Purchase #5	$151.88	5.617%	$160.4111	$160.41	$160.40	$160.40
Purchase #6	$220.67	11.188%	$245.3586	$245.36	$245.35	$245.40
Purchase #7	$230.77	5.828%	$244.2193	$244.22	$244.20	$244.20
7 purchase totals =	$972.68		$1,061.3513	$1,061.35	$1,061.35	$1,061.30