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	$200.76	4.788%	$210.3724	$210.37	$210.35	$210.40
Purchase #2	$166.65	3.304%	$172.1561	$172.16	$172.15	$172.20
Purchase #3	$178.83	13.625%	$203.1956	$203.20	$203.20	$203.20
Purchase #4	$150.74	11.792%	$168.5153	$168.52	$168.50	$168.50
Purchase #5	$67.60	8.511%	$73.3534	$73.35	$73.35	$73.40
Purchase #6	$76.62	7.337%	$82.2416	$82.24	$82.25	$82.20
Purchase #7	$140.63	9.860%	$154.4961	$154.50	$154.50	$154.50
7 purchase totals =	$981.83		$1,064.3305	$1,064.34	$1,064.30	$1,064.40