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	$175.26	13.717%	$199.3004	$199.30	$199.30	$199.30
Purchase #2	$123.50	9.118%	$134.7607	$134.76	$134.75	$134.80
Purchase #3	$57.34	11.354%	$63.8504	$63.85	$63.85	$63.90
Purchase #4	$56.51	10.322%	$62.343	$62.34	$62.35	$62.30
Purchase #5	$41.89	3.785%	$43.4755	$43.48	$43.50	$43.50
Purchase #6	$143.97	4.469%	$150.404	$150.40	$150.40	$150.40
Purchase #7	$77.58	6.558%	$82.6677	$82.67	$82.65	$82.70
7 purchase totals =	$676.05		$736.8017	$736.80	$736.80	$736.90