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	$69.36	5.135%	$72.9216	$72.92	$72.90	$72.90
Purchase #2	$42.29	11.504%	$47.155	$47.16	$47.15	$47.20
Purchase #3	$82.32	8.720%	$89.4983	$89.50	$89.50	$89.50
Purchase #4	$46.61	4.706%	$48.8035	$48.80	$48.80	$48.80
Purchase #5	$41.47	13.591%	$47.1062	$47.11	$47.10	$47.10
Purchase #6	$76.99	5.549%	$81.2622	$81.26	$81.25	$81.30
Purchase #7	$210.86	7.127%	$225.888	$225.89	$225.90	$225.90
7 purchase totals =	$569.90		$612.6348	$612.64	$612.60	$612.70