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	$120.35	3.261%	$124.2746	$124.27	$124.25	$124.30
Purchase #2	$7.43	6.423%	$7.9072	$7.91	$7.90	$7.90
Purchase #3	$191.63	6.761%	$204.5861	$204.59	$204.60	$204.60
Purchase #4	$32.84	13.486%	$37.2688	$37.27	$37.25	$37.30
Purchase #5	$72.49	13.130%	$82.0079	$82.01	$82.00	$82.00
Purchase #6	$246.92	6.182%	$262.1846	$262.18	$262.20	$262.20
Purchase #7	$99.77	6.438%	$106.1932	$106.19	$106.20	$106.20
7 purchase totals =	$771.43		$824.4224	$824.42	$824.40	$824.50