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	$142.38	10.862%	$157.8453	$157.85	$157.85	$157.80
Purchase #2	$131.27	12.663%	$147.8927	$147.89	$147.90	$147.90
Purchase #3	$209.66	7.517%	$225.4201	$225.42	$225.40	$225.40
Purchase #4	$224.42	13.410%	$254.5147	$254.51	$254.50	$254.50
Purchase #5	$119.89	13.499%	$136.074	$136.07	$136.05	$136.10
Purchase #6	$14.28	10.430%	$15.7694	$15.77	$15.75	$15.80
Purchase #7	$162.86	5.736%	$172.2016	$172.20	$172.20	$172.20
7 purchase totals =	$1,004.76		$1,109.7178	$1,109.71	$1,109.65	$1,109.70