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	$113.96	11.308%	$126.8466	$126.85	$126.85	$126.80
Purchase #2	$89.83	9.549%	$98.4079	$98.41	$98.40	$98.40
Purchase #3	$214.65	11.825%	$240.0324	$240.03	$240.05	$240.00
Purchase #4	$161.41	6.431%	$171.7903	$171.79	$171.80	$171.80
Purchase #5	$127.78	10.394%	$141.0615	$141.06	$141.05	$141.10
Purchase #6	$121.89	4.844%	$127.7944	$127.79	$127.80	$127.80
Purchase #7	$56.94	6.464%	$60.6206	$60.62	$60.60	$60.60
7 purchase totals =	$886.46		$966.5537	$966.55	$966.55	$966.50