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	$72.74	8.292%	$78.7716	$78.77	$78.75	$78.80
Purchase #2	$185.39	12.568%	$208.6898	$208.69	$208.70	$208.70
Purchase #3	$45.82	11.327%	$51.01	$51.01	$51.00	$51.00
Purchase #4	$217.42	11.562%	$242.5581	$242.56	$242.55	$242.60
Purchase #5	$108.68	8.744%	$118.183	$118.18	$118.20	$118.20
Purchase #6	$146.91	13.391%	$166.5827	$166.58	$166.60	$166.60
Purchase #7	$184.77	3.534%	$191.2998	$191.30	$191.30	$191.30
7 purchase totals =	$961.73		$1,057.0950	$1,057.09	$1,057.10	$1,057.20