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	$82.70	6.149%	$87.7852	$87.79	$87.80	$87.80
Purchase #2	$143.60	9.185%	$156.7897	$156.79	$156.80	$156.80
Purchase #3	$167.75	11.174%	$186.4944	$186.49	$186.50	$186.50
Purchase #4	$154.69	10.699%	$171.2403	$171.24	$171.25	$171.20
Purchase #5	$207.37	4.612%	$216.9339	$216.93	$216.95	$216.90
Purchase #6	$211.70	6.242%	$224.9143	$224.91	$224.90	$224.90
Purchase #7	$35.65	13.343%	$40.4068	$40.41	$40.40	$40.40
7 purchase totals =	$1,003.46		$1,084.5646	$1,084.56	$1,084.60	$1,084.50