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	$148.30	9.627%	$162.5768	$162.58	$162.60	$162.60
Purchase #2	$40.64	4.597%	$42.5082	$42.51	$42.50	$42.50
Purchase #3	$88.28	5.159%	$92.8344	$92.83	$92.85	$92.80
Purchase #4	$194.73	10.149%	$214.4931	$214.49	$214.50	$214.50
Purchase #5	$89.78	10.254%	$98.986	$98.99	$99.00	$99.00
Purchase #6	$205.58	13.263%	$232.8461	$232.85	$232.85	$232.80
Purchase #7	$83.54	11.661%	$93.2816	$93.28	$93.30	$93.30
7 purchase totals =	$850.85		$937.5262	$937.53	$937.60	$937.50