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	$111.32	11.872%	$124.5359	$124.54	$124.55	$124.50
Purchase #2	$91.55	11.295%	$101.8906	$101.89	$101.90	$101.90
Purchase #3	$149.83	8.211%	$162.1325	$162.13	$162.15	$162.10
Purchase #4	$24.30	13.580%	$27.5999	$27.60	$27.60	$27.60
Purchase #5	$94.48	6.155%	$100.2952	$100.30	$100.30	$100.30
Purchase #6	$213.98	12.367%	$240.4429	$240.44	$240.45	$240.40
Purchase #7	$67.46	5.723%	$71.3207	$71.32	$71.30	$71.30
7 purchase totals =	$752.92		$828.2177	$828.22	$828.25	$828.10