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	$168.65	4.449%	$176.1532	$176.15	$176.15	$176.20
Purchase #2	$242.82	10.479%	$268.2651	$268.27	$268.25	$268.30
Purchase #3	$32.66	7.346%	$35.0592	$35.06	$35.05	$35.10
Purchase #4	$17.28	9.650%	$18.9475	$18.95	$18.95	$18.90
Purchase #5	$95.60	4.757%	$100.1477	$100.15	$100.15	$100.10
Purchase #6	$131.33	6.532%	$139.9085	$139.91	$139.90	$139.90
Purchase #7	$29.61	10.716%	$32.783	$32.78	$32.80	$32.80
7 purchase totals =	$717.95		$771.2642	$771.27	$771.25	$771.30