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	$132.64	13.741%	$150.8661	$150.87	$150.85	$150.90
Purchase #2	$25.50	9.381%	$27.8922	$27.89	$27.90	$27.90
Purchase #3	$71.80	10.724%	$79.4998	$79.50	$79.50	$79.50
Purchase #4	$230.97	4.623%	$241.6477	$241.65	$241.65	$241.60
Purchase #5	$142.30	4.160%	$148.2197	$148.22	$148.20	$148.20
Purchase #6	$232.30	5.620%	$245.3553	$245.36	$245.35	$245.40
Purchase #7	$98.68	10.628%	$109.1677	$109.17	$109.15	$109.20
7 purchase totals =	$934.19		$1,002.6485	$1,002.66	$1,002.60	$1,002.70