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	$50.42	6.768%	$53.8324	$53.83	$53.85	$53.80
Purchase #2	$96.59	8.632%	$104.9276	$104.93	$104.95	$104.90
Purchase #3	$237.67	6.632%	$253.4323	$253.43	$253.45	$253.40
Purchase #4	$57.49	3.681%	$59.6062	$59.61	$59.60	$59.60
Purchase #5	$205.63	3.417%	$212.6564	$212.66	$212.65	$212.70
Purchase #6	$142.92	6.473%	$152.1712	$152.17	$152.15	$152.20
Purchase #7	$46.26	4.213%	$48.2089	$48.21	$48.20	$48.20
7 purchase totals =	$836.98		$884.8350	$884.84	$884.85	$884.80