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	$88.73	5.529%	$93.6359	$93.64	$93.65	$93.60
Purchase #2	$181.64	9.331%	$198.5888	$198.59	$198.60	$198.60
Purchase #3	$7.34	3.733%	$7.614	$7.61	$7.60	$7.60
Purchase #4	$39.70	6.841%	$42.4159	$42.42	$42.40	$42.40
Purchase #5	$101.77	10.584%	$112.5413	$112.54	$112.55	$112.50
Purchase #6	$226.77	13.231%	$256.7739	$256.77	$256.75	$256.80
Purchase #7	$44.49	6.401%	$47.3378	$47.34	$47.35	$47.30
7 purchase totals =	$690.44		$758.9076	$758.91	$758.90	$758.80