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	$156.81	10.182%	$172.7764	$172.78	$172.80	$172.80
Purchase #2	$232.39	9.363%	$254.1487	$254.15	$254.15	$254.10
Purchase #3	$89.53	11.656%	$99.9656	$99.97	$99.95	$100.00
Purchase #4	$164.84	8.104%	$178.1986	$178.20	$178.20	$178.20
Purchase #5	$46.49	11.111%	$51.6555	$51.66	$51.65	$51.70
Purchase #6	$58.51	10.353%	$64.5675	$64.57	$64.55	$64.60
Purchase #7	$175.85	7.254%	$188.6062	$188.61	$188.60	$188.60
7 purchase totals =	$924.42		$1,009.9185	$1,009.94	$1,009.90	$1,010.00