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	$52.40	6.562%	$55.8385	$55.84	$55.85	$55.80
Purchase #2	$26.51	7.409%	$28.4741	$28.47	$28.45	$28.50
Purchase #3	$241.32	11.427%	$268.8956	$268.90	$268.90	$268.90
Purchase #4	$169.28	13.543%	$192.2056	$192.21	$192.20	$192.20
Purchase #5	$214.51	10.728%	$237.5226	$237.52	$237.50	$237.50
Purchase #6	$76.44	5.421%	$80.5838	$80.58	$80.60	$80.60
Purchase #7	$136.79	13.741%	$155.5863	$155.59	$155.60	$155.60
7 purchase totals =	$917.25		$1,019.1065	$1,019.11	$1,019.10	$1,019.10