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	$39.92	7.284%	$42.8278	$42.83	$42.85	$42.80
Purchase #2	$70.43	4.464%	$73.574	$73.57	$73.55	$73.60
Purchase #3	$71.34	12.108%	$79.9778	$79.98	$80.00	$80.00
Purchase #4	$54.47	12.242%	$61.1382	$61.14	$61.15	$61.10
Purchase #5	$186.25	5.306%	$196.1324	$196.13	$196.15	$196.10
Purchase #6	$217.47	4.836%	$227.9868	$227.99	$228.00	$228.00
Purchase #7	$110.59	13.309%	$125.3084	$125.31	$125.30	$125.30
7 purchase totals =	$750.47		$806.9454	$806.95	$807.00	$806.90