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	$86.94	7.676%	$93.6135	$93.61	$93.60	$93.60
Purchase #2	$32.69	4.320%	$34.1022	$34.10	$34.10	$34.10
Purchase #3	$18.53	10.566%	$20.4879	$20.49	$20.50	$20.50
Purchase #4	$242.72	5.197%	$255.3342	$255.33	$255.35	$255.30
Purchase #5	$237.53	3.116%	$244.9314	$244.93	$244.95	$244.90
Purchase #6	$82.53	3.165%	$85.1421	$85.14	$85.15	$85.10
Purchase #7	$61.30	7.511%	$65.9042	$65.90	$65.90	$65.90
7 purchase totals =	$762.24		$799.5155	$799.50	$799.55	$799.40