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	$59.81	8.372%	$64.8173	$64.82	$64.80	$64.80
Purchase #2	$59.49	3.852%	$61.7816	$61.78	$61.80	$61.80
Purchase #3	$174.53	10.349%	$192.5921	$192.59	$192.60	$192.60
Purchase #4	$236.62	4.751%	$247.8618	$247.86	$247.85	$247.90
Purchase #5	$28.48	10.732%	$31.5365	$31.54	$31.55	$31.50
Purchase #6	$78.41	12.301%	$88.0552	$88.06	$88.05	$88.10
Purchase #7	$38.64	3.179%	$39.8684	$39.87	$39.85	$39.90
7 purchase totals =	$675.98		$726.5129	$726.52	$726.50	$726.60