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	$214.51	10.794%	$237.6642	$237.66	$237.65	$237.70
Purchase #2	$20.43	6.579%	$21.7741	$21.77	$21.75	$21.80
Purchase #3	$82.67	10.406%	$91.2726	$91.27	$91.25	$91.30
Purchase #4	$66.32	10.751%	$73.4501	$73.45	$73.45	$73.50
Purchase #5	$143.27	5.330%	$150.9063	$150.91	$150.90	$150.90
Purchase #6	$211.87	3.358%	$218.9846	$218.98	$219.00	$219.00
Purchase #7	$185.76	7.215%	$199.1626	$199.16	$199.15	$199.20
7 purchase totals =	$924.83		$993.2145	$993.20	$993.15	$993.40