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	$78.81	9.490%	$86.2891	$86.29	$86.30	$86.30
Purchase #2	$12.40	7.236%	$13.2973	$13.30	$13.30	$13.30
Purchase #3	$186.79	5.302%	$196.6936	$196.69	$196.70	$196.70
Purchase #4	$158.37	13.576%	$179.8703	$179.87	$179.85	$179.90
Purchase #5	$173.54	6.103%	$184.1311	$184.13	$184.15	$184.10
Purchase #6	$204.96	11.148%	$227.8089	$227.81	$227.80	$227.80
Purchase #7	$33.61	12.263%	$37.7316	$37.73	$37.75	$37.70
7 purchase totals =	$848.48		$925.8219	$925.82	$925.85	$925.80