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	$85.52	6.489%	$91.0694	$91.07	$91.05	$91.10
Purchase #2	$58.30	5.407%	$61.4523	$61.45	$61.45	$61.50
Purchase #3	$76.38	12.297%	$85.7724	$85.77	$85.75	$85.80
Purchase #4	$18.93	4.456%	$19.7735	$19.77	$19.75	$19.80
Purchase #5	$122.71	11.116%	$136.3504	$136.35	$136.35	$136.40
Purchase #6	$73.80	12.148%	$82.7652	$82.77	$82.75	$82.80
Purchase #7	$7.33	3.180%	$7.5631	$7.56	$7.55	$7.60
7 purchase totals =	$442.97		$484.7463	$484.74	$484.65	$485.00