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	$64.89	11.346%	$72.2524	$72.25	$72.25	$72.30
Purchase #2	$154.96	8.733%	$168.4927	$168.49	$168.50	$168.50
Purchase #3	$10.76	4.708%	$11.2666	$11.27	$11.25	$11.30
Purchase #4	$172.39	4.158%	$179.558	$179.56	$179.55	$179.60
Purchase #5	$93.47	6.107%	$99.1782	$99.18	$99.20	$99.20
Purchase #6	$34.49	13.651%	$39.1982	$39.20	$39.20	$39.20
Purchase #7	$28.55	4.685%	$29.8876	$29.89	$29.90	$29.90
7 purchase totals =	$559.51		$599.8337	$599.84	$599.85	$600.00