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	$169.51	5.162%	$178.2601	$178.26	$178.25	$178.30
Purchase #2	$77.64	7.524%	$83.4816	$83.48	$83.50	$83.50
Purchase #3	$205.35	3.723%	$212.9952	$213.00	$213.00	$213.00
Purchase #4	$78.62	13.735%	$89.4185	$89.42	$89.40	$89.40
Purchase #5	$187.25	13.747%	$212.9913	$212.99	$213.00	$213.00
Purchase #6	$144.36	5.221%	$151.897	$151.90	$151.90	$151.90
Purchase #7	$146.40	5.803%	$154.8956	$154.90	$154.90	$154.90
7 purchase totals =	$1,009.13		$1,083.9393	$1,083.95	$1,083.95	$1,084.00