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	$43.54	11.156%	$48.3973	$48.40	$48.40	$48.40
Purchase #2	$75.93	12.740%	$85.6035	$85.60	$85.60	$85.60
Purchase #3	$85.88	3.819%	$89.1598	$89.16	$89.15	$89.20
Purchase #4	$120.27	7.565%	$129.3684	$129.37	$129.35	$129.40
Purchase #5	$189.91	13.549%	$215.6409	$215.64	$215.65	$215.60
Purchase #6	$107.43	4.841%	$112.6307	$112.63	$112.65	$112.60
Purchase #7	$38.83	9.534%	$42.5321	$42.53	$42.55	$42.50
7 purchase totals =	$661.79		$723.3327	$723.33	$723.35	$723.30