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	$145.75	4.568%	$152.4079	$152.41	$152.40	$152.40
Purchase #2	$182.87	4.373%	$190.8669	$190.87	$190.85	$190.90
Purchase #3	$21.48	7.617%	$23.1161	$23.12	$23.10	$23.10
Purchase #4	$12.98	3.611%	$13.4487	$13.45	$13.45	$13.40
Purchase #5	$38.81	10.600%	$42.9239	$42.92	$42.90	$42.90
Purchase #6	$219.86	3.656%	$227.8981	$227.90	$227.90	$227.90
Purchase #7	$35.71	8.759%	$38.8378	$38.84	$38.85	$38.80
7 purchase totals =	$657.46		$689.4994	$689.51	$689.45	$689.40