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	$78.36	9.561%	$85.852	$85.85	$85.85	$85.90
Purchase #2	$6.68	10.452%	$7.3782	$7.38	$7.40	$7.40
Purchase #3	$54.25	5.513%	$57.2408	$57.24	$57.25	$57.20
Purchase #4	$168.72	6.602%	$179.8589	$179.86	$179.85	$179.90
Purchase #5	$80.73	12.118%	$90.5129	$90.51	$90.50	$90.50
Purchase #6	$223.98	9.318%	$244.8505	$244.85	$244.85	$244.90
Purchase #7	$100.54	6.232%	$106.8057	$106.81	$106.80	$106.80
7 purchase totals =	$713.26		$772.4990	$772.50	$772.50	$772.60