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	$197.66	10.508%	$218.4301	$218.43	$218.45	$218.40
Purchase #2	$79.32	7.502%	$85.2706	$85.27	$85.25	$85.30
Purchase #3	$146.28	11.442%	$163.0174	$163.02	$163.00	$163.00
Purchase #4	$152.92	11.813%	$170.9844	$170.98	$171.00	$171.00
Purchase #5	$80.88	5.611%	$85.4182	$85.42	$85.40	$85.40
Purchase #6	$126.49	4.166%	$131.7596	$131.76	$131.75	$131.80
Purchase #7	$139.95	6.216%	$148.6493	$148.65	$148.65	$148.60
7 purchase totals =	$923.50		$1,003.5296	$1,003.53	$1,003.50	$1,003.50