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	$142.86	9.822%	$156.8917	$156.89	$156.90	$156.90
Purchase #2	$192.79	4.210%	$200.9065	$200.91	$200.90	$200.90
Purchase #3	$239.95	13.399%	$272.1009	$272.10	$272.10	$272.10
Purchase #4	$123.52	4.155%	$128.6523	$128.65	$128.65	$128.70
Purchase #5	$35.42	3.293%	$36.5864	$36.59	$36.60	$36.60
Purchase #6	$151.96	12.513%	$170.9748	$170.97	$170.95	$171.00
Purchase #7	$227.85	12.444%	$256.2037	$256.20	$256.20	$256.20
7 purchase totals =	$1,114.35		$1,222.3163	$1,222.31	$1,222.30	$1,222.40