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	$194.97	8.268%	$211.0901	$211.09	$211.10	$211.10
Purchase #2	$238.61	6.372%	$253.8142	$253.81	$253.80	$253.80
Purchase #3	$47.35	11.170%	$52.639	$52.64	$52.65	$52.60
Purchase #4	$236.43	3.562%	$244.8516	$244.85	$244.85	$244.90
Purchase #5	$82.47	9.730%	$90.4943	$90.49	$90.50	$90.50
Purchase #6	$169.39	5.457%	$178.6336	$178.63	$178.65	$178.60
Purchase #7	$32.39	10.750%	$35.8719	$35.87	$35.85	$35.90
7 purchase totals =	$1,001.61		$1,067.3947	$1,067.38	$1,067.40	$1,067.40