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	$161.71	7.544%	$173.9094	$173.91	$173.90	$173.90
Purchase #2	$79.38	12.186%	$89.0532	$89.05	$89.05	$89.10
Purchase #3	$38.83	8.253%	$42.0346	$42.03	$42.05	$42.00
Purchase #4	$203.77	6.727%	$217.4776	$217.48	$217.50	$217.50
Purchase #5	$12.61	13.808%	$14.3512	$14.35	$14.35	$14.40
Purchase #6	$230.78	8.380%	$250.1194	$250.12	$250.10	$250.10
Purchase #7	$180.63	10.722%	$199.9971	$200.00	$200.00	$200.00
7 purchase totals =	$907.71		$986.9425	$986.94	$986.95	$987.00