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	$161.98	3.624%	$167.8502	$167.85	$167.85	$167.90
Purchase #2	$203.86	3.840%	$211.6882	$211.69	$211.70	$211.70
Purchase #3	$84.90	13.722%	$96.55	$96.55	$96.55	$96.60
Purchase #4	$132.84	7.111%	$142.2863	$142.29	$142.30	$142.30
Purchase #5	$244.33	13.580%	$277.51	$277.51	$277.50	$277.50
Purchase #6	$102.32	6.468%	$108.9381	$108.94	$108.95	$108.90
Purchase #7	$139.79	5.553%	$147.5525	$147.55	$147.55	$147.60
7 purchase totals =	$1,070.02		$1,152.3753	$1,152.38	$1,152.40	$1,152.50