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	$135.59	11.298%	$150.909	$150.91	$150.90	$150.90
Purchase #2	$46.87	7.102%	$50.1987	$50.20	$50.20	$50.20
Purchase #3	$89.61	12.554%	$100.8596	$100.86	$100.85	$100.90
Purchase #4	$124.34	7.546%	$133.7227	$133.72	$133.70	$133.70
Purchase #5	$207.32	12.629%	$233.5024	$233.50	$233.50	$233.50
Purchase #6	$20.25	6.497%	$21.5656	$21.57	$21.55	$21.60
Purchase #7	$89.49	5.580%	$94.4835	$94.48	$94.50	$94.50
7 purchase totals =	$713.47		$785.2415	$785.24	$785.20	$785.30