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	$168.56	10.139%	$185.6503	$185.65	$185.65	$185.70
Purchase #2	$144.56	10.389%	$159.5783	$159.58	$159.60	$159.60
Purchase #3	$127.60	6.728%	$136.1849	$136.18	$136.20	$136.20
Purchase #4	$30.34	8.421%	$32.8949	$32.89	$32.90	$32.90
Purchase #5	$200.28	10.859%	$222.0284	$222.03	$222.05	$222.00
Purchase #6	$90.67	7.155%	$97.1574	$97.16	$97.15	$97.20
Purchase #7	$231.41	6.191%	$245.7366	$245.74	$245.75	$245.70
7 purchase totals =	$993.42		$1,079.2308	$1,079.23	$1,079.30	$1,079.30