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	$227.63	10.391%	$251.283	$251.28	$251.30	$251.30
Purchase #2	$243.42	12.170%	$273.0442	$273.04	$273.05	$273.00
Purchase #3	$137.39	5.190%	$144.5205	$144.52	$144.50	$144.50
Purchase #4	$67.37	11.286%	$74.9734	$74.97	$74.95	$75.00
Purchase #5	$79.46	3.354%	$82.1251	$82.13	$82.15	$82.10
Purchase #6	$95.84	3.181%	$98.8887	$98.89	$98.90	$98.90
Purchase #7	$89.90	11.211%	$99.9787	$99.98	$100.00	$100.00
7 purchase totals =	$941.01		$1,024.8136	$1,024.81	$1,024.85	$1,024.80