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	$162.53	10.657%	$179.8508	$179.85	$179.85	$179.90
Purchase #2	$144.48	4.395%	$150.8299	$150.83	$150.85	$150.80
Purchase #3	$9.64	6.804%	$10.2959	$10.30	$10.30	$10.30
Purchase #4	$49.99	9.138%	$54.5581	$54.56	$54.55	$54.60
Purchase #5	$139.42	11.361%	$155.2595	$155.26	$155.25	$155.30
Purchase #6	$170.76	9.618%	$187.1837	$187.18	$187.20	$187.20
Purchase #7	$27.83	12.377%	$31.2745	$31.27	$31.25	$31.30
7 purchase totals =	$704.65		$769.2524	$769.25	$769.25	$769.40