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	$47.82	9.452%	$52.3399	$52.34	$52.35	$52.30
Purchase #2	$59.33	7.748%	$63.9269	$63.93	$63.95	$63.90
Purchase #3	$82.94	9.783%	$91.054	$91.05	$91.05	$91.10
Purchase #4	$55.69	8.771%	$60.5746	$60.57	$60.55	$60.60
Purchase #5	$19.56	6.813%	$20.8926	$20.89	$20.90	$20.90
Purchase #6	$167.61	9.866%	$184.1464	$184.15	$184.15	$184.10
Purchase #7	$130.34	12.615%	$146.7824	$146.78	$146.80	$146.80
7 purchase totals =	$563.29		$619.7168	$619.71	$619.75	$619.70