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	$127.25	11.428%	$141.7921	$141.79	$141.80	$141.80
Purchase #2	$72.72	9.362%	$79.528	$79.53	$79.55	$79.50
Purchase #3	$94.52	11.733%	$105.61	$105.61	$105.60	$105.60
Purchase #4	$148.25	13.424%	$168.1511	$168.15	$168.15	$168.20
Purchase #5	$244.65	7.426%	$262.8177	$262.82	$262.80	$262.80
Purchase #6	$204.54	11.391%	$227.8392	$227.84	$227.85	$227.80
Purchase #7	$166.43	13.618%	$189.0944	$189.09	$189.10	$189.10
7 purchase totals =	$1,058.36		$1,174.8325	$1,174.83	$1,174.85	$1,174.80