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	$96.55	7.618%	$103.9052	$103.91	$103.90	$103.90
Purchase #2	$136.32	7.841%	$147.0089	$147.01	$147.00	$147.00
Purchase #3	$123.58	8.467%	$134.0435	$134.04	$134.05	$134.00
Purchase #4	$164.31	9.224%	$179.466	$179.47	$179.45	$179.50
Purchase #5	$139.73	5.160%	$146.9401	$146.94	$146.95	$146.90
Purchase #6	$117.63	6.330%	$125.076	$125.08	$125.10	$125.10
Purchase #7	$50.73	7.179%	$54.3719	$54.37	$54.35	$54.40
7 purchase totals =	$828.85		$890.8116	$890.82	$890.80	$890.80