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	$216.66	8.825%	$235.7802	$235.78	$235.80	$235.80
Purchase #2	$54.82	3.275%	$56.6154	$56.62	$56.60	$56.60
Purchase #3	$39.43	9.334%	$43.1104	$43.11	$43.10	$43.10
Purchase #4	$16.96	12.111%	$19.014	$19.01	$19.00	$19.00
Purchase #5	$128.77	11.530%	$143.6172	$143.62	$143.60	$143.60
Purchase #6	$175.44	3.486%	$181.5558	$181.56	$181.55	$181.60
Purchase #7	$81.34	10.506%	$89.8856	$89.89	$89.90	$89.90
7 purchase totals =	$713.42		$769.5786	$769.59	$769.55	$769.60