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	$109.93	5.775%	$116.2785	$116.28	$116.30	$116.30
Purchase #2	$103.60	12.562%	$116.6142	$116.61	$116.60	$116.60
Purchase #3	$100.84	5.550%	$106.4366	$106.44	$106.45	$106.40
Purchase #4	$96.53	4.567%	$100.9385	$100.94	$100.95	$100.90
Purchase #5	$93.73	7.559%	$100.8151	$100.82	$100.80	$100.80
Purchase #6	$236.87	10.267%	$261.1894	$261.19	$261.20	$261.20
Purchase #7	$191.48	10.448%	$211.4858	$211.49	$211.50	$211.50
7 purchase totals =	$932.98		$1,013.7581	$1,013.77	$1,013.80	$1,013.70