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	$85.64	4.691%	$89.6574	$89.66	$89.65	$89.70
Purchase #2	$79.65	13.428%	$90.3454	$90.35	$90.35	$90.30
Purchase #3	$173.80	13.653%	$197.5289	$197.53	$197.55	$197.50
Purchase #4	$161.46	11.706%	$180.3605	$180.36	$180.35	$180.40
Purchase #5	$90.86	8.372%	$98.4668	$98.47	$98.45	$98.50
Purchase #6	$62.86	5.655%	$66.4147	$66.41	$66.40	$66.40
Purchase #7	$124.60	3.262%	$128.6645	$128.66	$128.65	$128.70
7 purchase totals =	$778.87		$851.4382	$851.44	$851.40	$851.50