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	$123.48	7.844%	$133.1658	$133.17	$133.15	$133.20
Purchase #2	$123.50	6.764%	$131.8535	$131.85	$131.85	$131.90
Purchase #3	$43.97	8.172%	$47.5632	$47.56	$47.55	$47.60
Purchase #4	$227.38	3.124%	$234.4834	$234.48	$234.50	$234.50
Purchase #5	$242.67	3.737%	$251.7386	$251.74	$251.75	$251.70
Purchase #6	$230.34	11.515%	$256.8637	$256.86	$256.85	$256.90
Purchase #7	$45.48	4.740%	$47.6358	$47.64	$47.65	$47.60
7 purchase totals =	$1,036.82		$1,103.3040	$1,103.30	$1,103.30	$1,103.40