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	$241.81	6.787%	$258.2216	$258.22	$258.20	$258.20
Purchase #2	$86.96	6.351%	$92.4828	$92.48	$92.50	$92.50
Purchase #3	$158.26	6.162%	$168.012	$168.01	$168.00	$168.00
Purchase #4	$63.27	4.372%	$66.0362	$66.04	$66.05	$66.00
Purchase #5	$241.88	11.166%	$268.8883	$268.89	$268.90	$268.90
Purchase #6	$182.52	4.450%	$190.6421	$190.64	$190.65	$190.60
Purchase #7	$136.91	13.425%	$155.2902	$155.29	$155.30	$155.30
7 purchase totals =	$1,111.61		$1,199.5732	$1,199.57	$1,199.60	$1,199.50