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	$126.53	10.300%	$139.5626	$139.56	$139.55	$139.60
Purchase #2	$121.33	13.604%	$137.8357	$137.84	$137.85	$137.80
Purchase #3	$22.46	11.829%	$25.1168	$25.12	$25.10	$25.10
Purchase #4	$79.34	4.661%	$83.038	$83.04	$83.05	$83.00
Purchase #5	$142.99	6.782%	$152.6876	$152.69	$152.70	$152.70
Purchase #6	$113.76	12.492%	$127.9709	$127.97	$127.95	$128.00
Purchase #7	$83.52	11.679%	$93.2743	$93.27	$93.25	$93.30
7 purchase totals =	$689.93		$759.4859	$759.49	$759.45	$759.50