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	$57.62	3.835%	$59.8297	$59.83	$59.85	$59.80
Purchase #2	$138.77	3.747%	$143.9697	$143.97	$143.95	$144.00
Purchase #3	$6.78	10.375%	$7.4834	$7.48	$7.50	$7.50
Purchase #4	$240.36	12.697%	$270.8785	$270.88	$270.90	$270.90
Purchase #5	$181.89	3.125%	$187.5741	$187.57	$187.55	$187.60
Purchase #6	$41.41	5.800%	$43.8118	$43.81	$43.80	$43.80
Purchase #7	$64.71	13.227%	$73.2692	$73.27	$73.25	$73.30
7 purchase totals =	$731.54		$786.8164	$786.81	$786.80	$786.90