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	$185.30	7.405%	$199.0215	$199.02	$199.00	$199.00
Purchase #2	$82.41	8.529%	$89.4387	$89.44	$89.45	$89.40
Purchase #3	$85.86	5.307%	$90.4166	$90.42	$90.40	$90.40
Purchase #4	$213.29	6.562%	$227.2861	$227.29	$227.30	$227.30
Purchase #5	$52.94	12.555%	$59.5866	$59.59	$59.60	$59.60
Purchase #6	$228.68	11.199%	$254.2899	$254.29	$254.30	$254.30
Purchase #7	$204.42	5.625%	$215.9186	$215.92	$215.90	$215.90
7 purchase totals =	$1,052.90		$1,135.9580	$1,135.97	$1,135.95	$1,135.90