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	$148.60	11.461%	$165.631	$165.63	$165.65	$165.60
Purchase #2	$31.29	3.119%	$32.2659	$32.27	$32.25	$32.30
Purchase #3	$144.60	6.572%	$154.1031	$154.10	$154.10	$154.10
Purchase #4	$204.43	13.426%	$231.8768	$231.88	$231.90	$231.90
Purchase #5	$83.71	8.666%	$90.9643	$90.96	$90.95	$91.00
Purchase #6	$53.71	10.868%	$59.5472	$59.55	$59.55	$59.50
Purchase #7	$37.98	3.834%	$39.4362	$39.44	$39.45	$39.40
7 purchase totals =	$704.32		$773.8245	$773.83	$773.85	$773.80