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	$86.57	3.547%	$89.6406	$89.64	$89.65	$89.60
Purchase #2	$59.42	6.170%	$63.0862	$63.09	$63.10	$63.10
Purchase #3	$55.58	10.726%	$61.5415	$61.54	$61.55	$61.50
Purchase #4	$237.44	7.179%	$254.4858	$254.49	$254.50	$254.50
Purchase #5	$50.33	13.777%	$57.264	$57.26	$57.25	$57.30
Purchase #6	$234.47	5.482%	$247.3236	$247.32	$247.30	$247.30
Purchase #7	$241.52	12.221%	$271.0362	$271.04	$271.05	$271.00
7 purchase totals =	$965.33		$1,044.3779	$1,044.38	$1,044.40	$1,044.30