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	$146.56	4.468%	$153.1083	$153.11	$153.10	$153.10
Purchase #2	$201.45	13.108%	$227.8561	$227.86	$227.85	$227.90
Purchase #3	$26.90	5.150%	$28.2854	$28.29	$28.30	$28.30
Purchase #4	$201.54	6.775%	$215.1943	$215.19	$215.20	$215.20
Purchase #5	$148.72	10.292%	$164.0263	$164.03	$164.05	$164.00
Purchase #6	$172.37	10.467%	$190.412	$190.41	$190.40	$190.40
Purchase #7	$113.37	8.798%	$123.3443	$123.34	$123.35	$123.30
7 purchase totals =	$1,010.91		$1,102.2267	$1,102.23	$1,102.25	$1,102.20