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	$100.43	11.555%	$112.0347	$112.03	$112.05	$112.00
Purchase #2	$206.72	3.368%	$213.6823	$213.68	$213.70	$213.70
Purchase #3	$105.46	4.263%	$109.9558	$109.96	$109.95	$110.00
Purchase #4	$40.59	4.719%	$42.5054	$42.51	$42.50	$42.50
Purchase #5	$189.60	3.172%	$195.6141	$195.61	$195.60	$195.60
Purchase #6	$99.97	5.118%	$105.0865	$105.09	$105.10	$105.10
Purchase #7	$5.26	5.228%	$5.535	$5.54	$5.55	$5.50
7 purchase totals =	$748.03		$784.4138	$784.42	$784.45	$784.40