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	$200.92	4.524%	$210.0096	$210.01	$210.00	$210.00
Purchase #2	$73.69	12.762%	$83.0943	$83.09	$83.10	$83.10
Purchase #3	$226.59	12.136%	$254.089	$254.09	$254.10	$254.10
Purchase #4	$235.38	4.543%	$246.0733	$246.07	$246.05	$246.10
Purchase #5	$132.40	6.498%	$141.0034	$141.00	$141.00	$141.00
Purchase #6	$84.37	6.107%	$89.5225	$89.52	$89.50	$89.50
Purchase #7	$28.61	13.303%	$32.416	$32.42	$32.40	$32.40
7 purchase totals =	$981.96		$1,056.2081	$1,056.20	$1,056.15	$1,056.20