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	$241.39	10.206%	$266.0263	$266.03	$266.05	$266.00
Purchase #2	$80.65	11.175%	$89.6626	$89.66	$89.65	$89.70
Purchase #3	$51.30	3.386%	$53.037	$53.04	$53.05	$53.00
Purchase #4	$165.52	13.874%	$188.4842	$188.48	$188.50	$188.50
Purchase #5	$145.78	3.372%	$150.6957	$150.70	$150.70	$150.70
Purchase #6	$34.73	11.244%	$38.635	$38.64	$38.65	$38.60
Purchase #7	$61.93	4.378%	$64.6413	$64.64	$64.65	$64.60
7 purchase totals =	$781.30		$851.1821	$851.19	$851.25	$851.10