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	$196.47	13.454%	$222.9031	$222.90	$222.90	$222.90
Purchase #2	$20.39	7.194%	$21.8569	$21.86	$21.85	$21.90
Purchase #3	$119.25	11.155%	$132.5523	$132.55	$132.55	$132.60
Purchase #4	$52.89	5.329%	$55.7085	$55.71	$55.70	$55.70
Purchase #5	$48.30	8.527%	$52.4185	$52.42	$52.40	$52.40
Purchase #6	$70.63	13.686%	$80.2964	$80.30	$80.30	$80.30
Purchase #7	$85.37	7.415%	$91.7002	$91.70	$91.70	$91.70
7 purchase totals =	$593.30		$657.4359	$657.44	$657.40	$657.50