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	$68.91	13.728%	$78.37	$78.37	$78.35	$78.40
Purchase #2	$58.48	10.778%	$64.783	$64.78	$64.80	$64.80
Purchase #3	$127.87	3.843%	$132.784	$132.78	$132.80	$132.80
Purchase #4	$71.53	6.257%	$76.0056	$76.01	$76.00	$76.00
Purchase #5	$151.69	4.529%	$158.56	$158.56	$158.55	$158.60
Purchase #6	$201.97	3.686%	$209.4146	$209.41	$209.40	$209.40
Purchase #7	$137.85	10.102%	$151.7756	$151.78	$151.80	$151.80
7 purchase totals =	$818.30		$871.6928	$871.69	$871.70	$871.80