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	$132.43	7.438%	$142.2801	$142.28	$142.30	$142.30
Purchase #2	$152.91	8.488%	$165.889	$165.89	$165.90	$165.90
Purchase #3	$87.64	11.789%	$97.9719	$97.97	$97.95	$98.00
Purchase #4	$114.85	12.395%	$129.0857	$129.09	$129.10	$129.10
Purchase #5	$178.39	7.230%	$191.2876	$191.29	$191.30	$191.30
Purchase #6	$89.86	12.291%	$100.9047	$100.90	$100.90	$100.90
Purchase #7	$137.58	7.498%	$147.8957	$147.90	$147.90	$147.90
7 purchase totals =	$893.66		$975.3147	$975.32	$975.35	$975.40