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	$120.25	3.870%	$124.9037	$124.90	$124.90	$124.90
Purchase #2	$167.94	10.793%	$186.0658	$186.07	$186.05	$186.10
Purchase #3	$229.77	3.811%	$238.5265	$238.53	$238.55	$238.50
Purchase #4	$148.54	5.620%	$156.8879	$156.89	$156.90	$156.90
Purchase #5	$170.88	8.524%	$185.4458	$185.45	$185.45	$185.40
Purchase #6	$148.50	13.711%	$168.8608	$168.86	$168.85	$168.90
Purchase #7	$131.43	10.473%	$145.1947	$145.19	$145.20	$145.20
7 purchase totals =	$1,117.31		$1,205.8852	$1,205.89	$1,205.90	$1,205.90