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	$199.35	11.571%	$222.4168	$222.42	$222.40	$222.40
Purchase #2	$43.26	7.192%	$46.3713	$46.37	$46.35	$46.40
Purchase #3	$124.63	4.565%	$130.3194	$130.32	$130.30	$130.30
Purchase #4	$94.51	9.370%	$103.3656	$103.37	$103.35	$103.40
Purchase #5	$197.48	9.779%	$216.7916	$216.79	$216.80	$216.80
Purchase #6	$76.25	6.403%	$81.1323	$81.13	$81.15	$81.10
Purchase #7	$210.73	3.222%	$217.5197	$217.52	$217.50	$217.50
7 purchase totals =	$946.21		$1,017.9167	$1,017.92	$1,017.85	$1,017.90