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	$55.25	8.107%	$59.7291	$59.73	$59.75	$59.70
Purchase #2	$195.49	13.805%	$222.4774	$222.48	$222.50	$222.50
Purchase #3	$162.45	4.239%	$169.3363	$169.34	$169.35	$169.30
Purchase #4	$95.55	7.445%	$102.6637	$102.66	$102.65	$102.70
Purchase #5	$67.55	4.367%	$70.4999	$70.50	$70.50	$70.50
Purchase #6	$27.46	4.646%	$28.7358	$28.74	$28.75	$28.70
Purchase #7	$135.86	13.471%	$154.1617	$154.16	$154.15	$154.20
7 purchase totals =	$739.61		$807.6039	$807.61	$807.65	$807.60