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	$69.75	6.738%	$74.4498	$74.45	$74.45	$74.40
Purchase #2	$191.56	10.417%	$211.5148	$211.51	$211.50	$211.50
Purchase #3	$122.93	11.247%	$136.7559	$136.76	$136.75	$136.80
Purchase #4	$118.94	3.559%	$123.1731	$123.17	$123.15	$123.20
Purchase #5	$214.61	6.348%	$228.2334	$228.23	$228.25	$228.20
Purchase #6	$214.74	12.857%	$242.3491	$242.35	$242.35	$242.30
Purchase #7	$79.54	5.378%	$83.8177	$83.82	$83.80	$83.80
7 purchase totals =	$1,012.07		$1,100.2938	$1,100.29	$1,100.25	$1,100.20