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	$72.79	3.517%	$75.35	$75.35	$75.35	$75.40
Purchase #2	$212.48	9.482%	$232.6274	$232.63	$232.65	$232.60
Purchase #3	$82.88	11.608%	$92.5007	$92.50	$92.50	$92.50
Purchase #4	$200.39	10.859%	$222.1504	$222.15	$222.15	$222.20
Purchase #5	$61.51	6.328%	$65.4024	$65.40	$65.40	$65.40
Purchase #6	$152.90	13.439%	$173.4482	$173.45	$173.45	$173.40
Purchase #7	$215.88	6.303%	$229.4869	$229.49	$229.50	$229.50
7 purchase totals =	$998.83		$1,090.9660	$1,090.97	$1,091.00	$1,091.00