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	$41.76	6.764%	$44.5846	$44.58	$44.60	$44.60
Purchase #2	$177.40	9.723%	$194.6486	$194.65	$194.65	$194.60
Purchase #3	$74.90	8.372%	$81.1706	$81.17	$81.15	$81.20
Purchase #4	$89.40	12.856%	$100.8933	$100.89	$100.90	$100.90
Purchase #5	$183.40	11.499%	$204.4892	$204.49	$204.50	$204.50
Purchase #6	$20.26	6.790%	$21.6357	$21.64	$21.65	$21.60
Purchase #7	$79.60	3.714%	$82.5563	$82.56	$82.55	$82.60
7 purchase totals =	$666.72		$729.9783	$729.98	$730.00	$730.00