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	$218.69	13.679%	$248.6046	$248.60	$248.60	$248.60
Purchase #2	$18.31	12.112%	$20.5277	$20.53	$20.55	$20.50
Purchase #3	$53.93	5.433%	$56.86	$56.86	$56.85	$56.90
Purchase #4	$16.77	6.536%	$17.8661	$17.87	$17.85	$17.90
Purchase #5	$79.27	7.577%	$85.2763	$85.28	$85.30	$85.30
Purchase #6	$231.37	8.392%	$250.7866	$250.79	$250.80	$250.80
Purchase #7	$44.88	12.433%	$50.4599	$50.46	$50.45	$50.50
7 purchase totals =	$663.22		$730.3812	$730.39	$730.40	$730.50