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	$131.90	11.271%	$146.7664	$146.77	$146.75	$146.80
Purchase #2	$167.61	9.408%	$183.3787	$183.38	$183.40	$183.40
Purchase #3	$156.50	6.481%	$166.6428	$166.64	$166.65	$166.60
Purchase #4	$94.59	6.500%	$100.7384	$100.74	$100.75	$100.70
Purchase #5	$30.44	5.182%	$32.0174	$32.02	$32.00	$32.00
Purchase #6	$148.53	7.305%	$159.3801	$159.38	$159.40	$159.40
Purchase #7	$94.59	3.199%	$97.6159	$97.62	$97.60	$97.60
7 purchase totals =	$824.16		$886.5397	$886.55	$886.55	$886.50