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	$176.52	13.439%	$200.2425	$200.24	$200.25	$200.20
Purchase #2	$213.75	11.442%	$238.2073	$238.21	$238.20	$238.20
Purchase #3	$56.88	6.364%	$60.4998	$60.50	$60.50	$60.50
Purchase #4	$124.62	10.661%	$137.9057	$137.91	$137.90	$137.90
Purchase #5	$117.73	10.729%	$130.3613	$130.36	$130.35	$130.40
Purchase #6	$225.63	13.160%	$255.3229	$255.32	$255.30	$255.30
Purchase #7	$70.30	3.745%	$72.9327	$72.93	$72.95	$72.90
7 purchase totals =	$985.43		$1,095.4722	$1,095.47	$1,095.45	$1,095.40