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	$82.45	10.838%	$91.3859	$91.39	$91.40	$91.40
Purchase #2	$135.78	8.462%	$147.2697	$147.27	$147.25	$147.30
Purchase #3	$48.43	13.149%	$54.7981	$54.80	$54.80	$54.80
Purchase #4	$162.51	5.553%	$171.5342	$171.53	$171.55	$171.50
Purchase #5	$198.96	8.207%	$215.2886	$215.29	$215.30	$215.30
Purchase #6	$203.83	13.468%	$231.2818	$231.28	$231.30	$231.30
Purchase #7	$196.49	6.538%	$209.3365	$209.34	$209.35	$209.30
7 purchase totals =	$1,028.45		$1,120.8948	$1,120.90	$1,120.95	$1,120.90