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	$182.55	10.819%	$202.3001	$202.30	$202.30	$202.30
Purchase #2	$6.97	7.498%	$7.4926	$7.49	$7.50	$7.50
Purchase #3	$202.37	6.472%	$215.4674	$215.47	$215.45	$215.50
Purchase #4	$144.36	12.717%	$162.7183	$162.72	$162.70	$162.70
Purchase #5	$70.89	8.753%	$77.095	$77.10	$77.10	$77.10
Purchase #6	$55.82	7.220%	$59.8502	$59.85	$59.85	$59.90
Purchase #7	$247.81	10.790%	$274.5487	$274.55	$274.55	$274.50
7 purchase totals =	$910.77		$999.4723	$999.48	$999.45	$999.50