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	$152.49	8.428%	$165.3419	$165.34	$165.35	$165.30
Purchase #2	$75.92	8.434%	$82.3231	$82.32	$82.30	$82.30
Purchase #3	$53.56	11.733%	$59.8442	$59.84	$59.85	$59.80
Purchase #4	$31.32	6.367%	$33.3141	$33.31	$33.30	$33.30
Purchase #5	$128.59	11.849%	$143.8266	$143.83	$143.85	$143.80
Purchase #6	$73.49	13.154%	$83.1569	$83.16	$83.15	$83.20
Purchase #7	$100.91	12.142%	$113.1625	$113.16	$113.15	$113.20
7 purchase totals =	$616.28		$680.9693	$680.96	$680.95	$680.90