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	$200.62	7.422%	$215.51	$215.51	$215.50	$215.50
Purchase #2	$39.50	8.505%	$42.8595	$42.86	$42.85	$42.90
Purchase #3	$157.84	6.368%	$167.8913	$167.89	$167.90	$167.90
Purchase #4	$114.98	3.414%	$118.9054	$118.91	$118.90	$118.90
Purchase #5	$152.48	12.646%	$171.7626	$171.76	$171.75	$171.80
Purchase #6	$92.65	6.535%	$98.7047	$98.70	$98.70	$98.70
Purchase #7	$57.57	5.472%	$60.7202	$60.72	$60.70	$60.70
7 purchase totals =	$815.64		$876.3537	$876.35	$876.30	$876.40