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	$55.43	7.333%	$59.4947	$59.49	$59.50	$59.50
Purchase #2	$15.56	4.453%	$16.2529	$16.25	$16.25	$16.30
Purchase #3	$39.90	8.135%	$43.1459	$43.15	$43.15	$43.10
Purchase #4	$27.33	11.352%	$30.4325	$30.43	$30.45	$30.40
Purchase #5	$149.54	12.637%	$168.4374	$168.44	$168.45	$168.40
Purchase #6	$68.94	6.534%	$73.4445	$73.44	$73.45	$73.40
Purchase #7	$154.90	5.155%	$162.8851	$162.89	$162.90	$162.90
7 purchase totals =	$511.60		$554.0930	$554.09	$554.15	$554.00