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	$167.52	9.496%	$183.4277	$183.43	$183.45	$183.40
Purchase #2	$113.41	13.607%	$128.8417	$128.84	$128.85	$128.80
Purchase #3	$32.80	9.609%	$35.9518	$35.95	$35.95	$36.00
Purchase #4	$98.39	11.331%	$109.5386	$109.54	$109.55	$109.50
Purchase #5	$29.56	6.370%	$31.443	$31.44	$31.45	$31.40
Purchase #6	$17.63	3.871%	$18.3125	$18.31	$18.30	$18.30
Purchase #7	$176.42	11.629%	$196.9359	$196.94	$196.95	$196.90
7 purchase totals =	$635.73		$704.4512	$704.45	$704.50	$704.30