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	$173.67	7.595%	$186.8602	$186.86	$186.85	$186.90
Purchase #2	$36.25	11.127%	$40.2835	$40.28	$40.30	$40.30
Purchase #3	$39.83	6.140%	$42.2756	$42.28	$42.30	$42.30
Purchase #4	$230.54	11.465%	$256.9714	$256.97	$256.95	$257.00
Purchase #5	$64.58	12.357%	$72.5602	$72.56	$72.55	$72.60
Purchase #6	$224.95	9.845%	$247.0963	$247.10	$247.10	$247.10
Purchase #7	$181.71	10.443%	$200.686	$200.69	$200.70	$200.70
7 purchase totals =	$951.53		$1,046.7332	$1,046.74	$1,046.75	$1,046.90