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	$130.96	10.417%	$144.6021	$144.60	$144.60	$144.60
Purchase #2	$41.31	5.219%	$43.466	$43.47	$43.45	$43.50
Purchase #3	$99.90	3.740%	$103.6363	$103.64	$103.65	$103.60
Purchase #4	$208.56	8.152%	$225.5618	$225.56	$225.55	$225.60
Purchase #5	$46.77	8.715%	$50.846	$50.85	$50.85	$50.80
Purchase #6	$38.34	9.461%	$41.9673	$41.97	$41.95	$42.00
Purchase #7	$67.48	13.424%	$76.5385	$76.54	$76.55	$76.50
7 purchase totals =	$633.32		$686.6180	$686.63	$686.60	$686.60