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	$152.79	8.657%	$166.017	$166.02	$166.00	$166.00
Purchase #2	$200.89	6.267%	$213.4798	$213.48	$213.50	$213.50
Purchase #3	$118.61	4.557%	$124.0151	$124.02	$124.00	$124.00
Purchase #4	$10.56	3.389%	$10.9179	$10.92	$10.90	$10.90
Purchase #5	$167.63	4.314%	$174.8616	$174.86	$174.85	$174.90
Purchase #6	$86.43	3.471%	$89.43	$89.43	$89.45	$89.40
Purchase #7	$138.30	10.505%	$152.8284	$152.83	$152.85	$152.80
7 purchase totals =	$875.21		$931.5498	$931.56	$931.55	$931.50