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	$247.80	9.713%	$271.8688	$271.87	$271.85	$271.90
Purchase #2	$34.73	3.326%	$35.8851	$35.89	$35.90	$35.90
Purchase #3	$13.43	11.827%	$15.0184	$15.02	$15.00	$15.00
Purchase #4	$73.51	6.365%	$78.1889	$78.19	$78.20	$78.20
Purchase #5	$191.92	7.498%	$206.3102	$206.31	$206.30	$206.30
Purchase #6	$96.73	4.836%	$101.4079	$101.41	$101.40	$101.40
Purchase #7	$31.31	6.817%	$33.4444	$33.44	$33.45	$33.40
7 purchase totals =	$689.43		$742.1237	$742.13	$742.10	$742.10