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	$55.96	5.505%	$59.0406	$59.04	$59.05	$59.00
Purchase #2	$15.72	12.745%	$17.7235	$17.72	$17.70	$17.70
Purchase #3	$89.26	10.618%	$98.7376	$98.74	$98.75	$98.70
Purchase #4	$69.81	3.586%	$72.3134	$72.31	$72.30	$72.30
Purchase #5	$144.64	5.352%	$152.3811	$152.38	$152.40	$152.40
Purchase #6	$149.66	8.751%	$162.7567	$162.76	$162.75	$162.80
Purchase #7	$147.39	4.443%	$153.9385	$153.94	$153.95	$153.90
7 purchase totals =	$672.44		$716.8914	$716.89	$716.90	$716.80