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	$175.31	12.185%	$196.6715	$196.67	$196.65	$196.70
Purchase #2	$242.68	7.603%	$261.131	$261.13	$261.15	$261.10
Purchase #3	$26.67	6.175%	$28.3169	$28.32	$28.30	$28.30
Purchase #4	$219.77	6.271%	$233.5518	$233.55	$233.55	$233.60
Purchase #5	$82.38	11.614%	$91.9476	$91.95	$91.95	$91.90
Purchase #6	$144.69	7.388%	$155.3797	$155.38	$155.40	$155.40
Purchase #7	$105.50	13.705%	$119.9588	$119.96	$119.95	$120.00
7 purchase totals =	$997.00		$1,086.9573	$1,086.96	$1,086.95	$1,087.00