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	$59.62	5.673%	$63.0022	$63.00	$63.00	$63.00
Purchase #2	$50.62	11.296%	$56.338	$56.34	$56.35	$56.30
Purchase #3	$34.39	7.850%	$37.0896	$37.09	$37.10	$37.10
Purchase #4	$73.72	11.799%	$82.4182	$82.42	$82.40	$82.40
Purchase #5	$71.31	3.557%	$73.8465	$73.85	$73.85	$73.80
Purchase #6	$88.48	12.611%	$99.6382	$99.64	$99.65	$99.60
Purchase #7	$145.52	12.785%	$164.1247	$164.12	$164.10	$164.10
7 purchase totals =	$523.66		$576.4574	$576.46	$576.45	$576.30