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	$209.90	13.317%	$237.8524	$237.85	$237.85	$237.90
Purchase #2	$43.26	6.220%	$45.9508	$45.95	$45.95	$46.00
Purchase #3	$135.83	8.447%	$147.3036	$147.30	$147.30	$147.30
Purchase #4	$109.80	7.313%	$117.8297	$117.83	$117.85	$117.80
Purchase #5	$93.43	13.108%	$105.6768	$105.68	$105.70	$105.70
Purchase #6	$136.89	6.392%	$145.64	$145.64	$145.65	$145.60
Purchase #7	$73.66	6.307%	$78.3057	$78.31	$78.30	$78.30
7 purchase totals =	$802.77		$878.5590	$878.56	$878.60	$878.60