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	$147.72	3.812%	$153.3511	$153.35	$153.35	$153.40
Purchase #2	$98.29	11.351%	$109.4469	$109.45	$109.45	$109.40
Purchase #3	$71.39	10.787%	$79.0908	$79.09	$79.10	$79.10
Purchase #4	$114.72	10.787%	$127.0948	$127.09	$127.10	$127.10
Purchase #5	$93.82	7.696%	$101.0404	$101.04	$101.05	$101.00
Purchase #6	$208.77	3.302%	$215.6636	$215.66	$215.65	$215.70
Purchase #7	$73.26	6.850%	$78.2783	$78.28	$78.30	$78.30
7 purchase totals =	$807.97		$863.9659	$863.96	$864.00	$864.00