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	$200.55	11.412%	$223.4368	$223.44	$223.45	$223.40
Purchase #2	$57.72	6.503%	$61.4735	$61.47	$61.45	$61.50
Purchase #3	$164.41	13.687%	$186.9128	$186.91	$186.90	$186.90
Purchase #4	$243.45	9.741%	$267.1645	$267.16	$267.15	$267.20
Purchase #5	$170.40	13.163%	$192.8298	$192.83	$192.85	$192.80
Purchase #6	$191.69	8.629%	$208.2309	$208.23	$208.25	$208.20
Purchase #7	$187.31	11.233%	$208.3505	$208.35	$208.35	$208.40
7 purchase totals =	$1,215.53		$1,348.3988	$1,348.39	$1,348.40	$1,348.40