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	$40.33	3.369%	$41.6887	$41.69	$41.70	$41.70
Purchase #2	$50.50	3.788%	$52.4129	$52.41	$52.40	$52.40
Purchase #3	$83.71	4.486%	$87.4652	$87.47	$87.45	$87.50
Purchase #4	$100.33	12.736%	$113.108	$113.11	$113.10	$113.10
Purchase #5	$126.83	6.811%	$135.4684	$135.47	$135.45	$135.50
Purchase #6	$20.28	3.244%	$20.9379	$20.94	$20.95	$20.90
Purchase #7	$185.85	7.808%	$200.3612	$200.36	$200.35	$200.40
7 purchase totals =	$607.83		$651.4423	$651.45	$651.40	$651.50