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	$199.90	7.670%	$215.2323	$215.23	$215.25	$215.20
Purchase #2	$28.89	8.789%	$31.4291	$31.43	$31.45	$31.40
Purchase #3	$176.61	7.148%	$189.2341	$189.23	$189.25	$189.20
Purchase #4	$37.40	11.166%	$41.5761	$41.58	$41.60	$41.60
Purchase #5	$166.93	13.134%	$188.8546	$188.85	$188.85	$188.90
Purchase #6	$19.37	12.459%	$21.7833	$21.78	$21.80	$21.80
Purchase #7	$133.63	11.629%	$149.1698	$149.17	$149.15	$149.20
7 purchase totals =	$762.73		$837.2793	$837.27	$837.35	$837.30