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	$225.45	5.228%	$237.2365	$237.24	$237.25	$237.20
Purchase #2	$68.41	9.265%	$74.7482	$74.75	$74.75	$74.70
Purchase #3	$65.41	11.236%	$72.7595	$72.76	$72.75	$72.80
Purchase #4	$37.96	10.218%	$41.8388	$41.84	$41.85	$41.80
Purchase #5	$134.32	7.558%	$144.4719	$144.47	$144.45	$144.50
Purchase #6	$92.47	6.377%	$98.3668	$98.37	$98.35	$98.40
Purchase #7	$76.34	8.557%	$82.8724	$82.87	$82.85	$82.90
7 purchase totals =	$700.36		$752.2941	$752.30	$752.25	$752.30