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	$112.54	13.805%	$128.0761	$128.08	$128.10	$128.10
Purchase #2	$244.35	12.743%	$275.4875	$275.49	$275.50	$275.50
Purchase #3	$180.64	8.724%	$196.399	$196.40	$196.40	$196.40
Purchase #4	$239.43	10.410%	$264.3547	$264.35	$264.35	$264.40
Purchase #5	$209.94	3.676%	$217.6574	$217.66	$217.65	$217.70
Purchase #6	$82.26	3.507%	$85.1449	$85.14	$85.15	$85.10
Purchase #7	$179.75	6.471%	$191.3816	$191.38	$191.40	$191.40
7 purchase totals =	$1,248.91		$1,358.5012	$1,358.50	$1,358.55	$1,358.60