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	$63.51	6.689%	$67.7582	$67.76	$67.75	$67.80
Purchase #2	$249.97	3.687%	$259.1864	$259.19	$259.20	$259.20
Purchase #3	$99.69	6.550%	$106.2197	$106.22	$106.20	$106.20
Purchase #4	$249.53	10.857%	$276.6215	$276.62	$276.60	$276.60
Purchase #5	$193.78	11.767%	$216.5821	$216.58	$216.60	$216.60
Purchase #6	$117.93	4.666%	$123.4326	$123.43	$123.45	$123.40
Purchase #7	$181.40	13.482%	$205.8563	$205.86	$205.85	$205.90
7 purchase totals =	$1,155.81		$1,255.6568	$1,255.66	$1,255.65	$1,255.70