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	$113.42	10.300%	$125.1023	$125.10	$125.10	$125.10
Purchase #2	$135.87	10.401%	$150.0018	$150.00	$150.00	$150.00
Purchase #3	$178.71	12.416%	$200.8986	$200.90	$200.90	$200.90
Purchase #4	$36.82	3.355%	$38.0553	$38.06	$38.05	$38.10
Purchase #5	$36.28	12.756%	$40.9079	$40.91	$40.90	$40.90
Purchase #6	$34.89	8.269%	$37.7751	$37.78	$37.80	$37.80
Purchase #7	$153.52	5.603%	$162.1217	$162.12	$162.10	$162.10
7 purchase totals =	$689.51		$754.8627	$754.87	$754.85	$754.90