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	$247.68	13.832%	$281.9391	$281.94	$281.95	$281.90
Purchase #2	$207.73	7.476%	$223.2599	$223.26	$223.25	$223.30
Purchase #3	$229.78	12.458%	$258.406	$258.41	$258.40	$258.40
Purchase #4	$178.48	3.523%	$184.7679	$184.77	$184.75	$184.80
Purchase #5	$94.41	6.378%	$100.4315	$100.43	$100.45	$100.40
Purchase #6	$37.48	5.253%	$39.4488	$39.45	$39.45	$39.40
Purchase #7	$72.68	13.148%	$82.236	$82.24	$82.25	$82.20
7 purchase totals =	$1,068.24		$1,170.4892	$1,170.50	$1,170.50	$1,170.40