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	$148.93	5.265%	$156.7712	$156.77	$156.75	$156.80
Purchase #2	$6.92	7.465%	$7.4366	$7.44	$7.45	$7.40
Purchase #3	$106.82	6.105%	$113.3414	$113.34	$113.35	$113.30
Purchase #4	$232.76	12.513%	$261.8853	$261.89	$261.90	$261.90
Purchase #5	$207.34	11.525%	$231.2359	$231.24	$231.25	$231.20
Purchase #6	$248.56	6.303%	$264.2267	$264.23	$264.25	$264.20
Purchase #7	$88.78	11.665%	$99.1362	$99.14	$99.15	$99.10
7 purchase totals =	$1,040.11		$1,134.0333	$1,134.05	$1,134.10	$1,133.90