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	$55.69	10.413%	$61.489	$61.49	$61.50	$61.50
Purchase #2	$58.48	4.219%	$60.9473	$60.95	$60.95	$60.90
Purchase #3	$74.84	7.633%	$80.5525	$80.55	$80.55	$80.60
Purchase #4	$185.86	4.844%	$194.8631	$194.86	$194.85	$194.90
Purchase #5	$51.34	11.833%	$57.4151	$57.42	$57.40	$57.40
Purchase #6	$109.79	7.385%	$117.898	$117.90	$117.90	$117.90
Purchase #7	$190.89	9.284%	$208.6122	$208.61	$208.60	$208.60
7 purchase totals =	$726.89		$781.7772	$781.78	$781.75	$781.80