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	$110.42	7.820%	$119.0548	$119.05	$119.05	$119.10
Purchase #2	$226.81	8.222%	$245.4583	$245.46	$245.45	$245.50
Purchase #3	$196.98	11.112%	$218.8684	$218.87	$218.85	$218.90
Purchase #4	$240.75	4.328%	$251.1697	$251.17	$251.15	$251.20
Purchase #5	$246.66	5.583%	$260.431	$260.43	$260.45	$260.40
Purchase #6	$55.72	12.871%	$62.8917	$62.89	$62.90	$62.90
Purchase #7	$99.41	4.111%	$103.4967	$103.50	$103.50	$103.50
7 purchase totals =	$1,176.75		$1,261.3706	$1,261.37	$1,261.35	$1,261.50