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	5.356%	$60.7061	$60.71	$60.70	$60.70
Purchase #2	$38.79	6.193%	$41.1923	$41.19	$41.20	$41.20
Purchase #3	$92.38	4.179%	$96.2406	$96.24	$96.25	$96.20
Purchase #4	$73.97	12.424%	$83.16	$83.16	$83.15	$83.20
Purchase #5	$90.48	4.529%	$94.5778	$94.58	$94.60	$94.60
Purchase #6	$56.78	5.467%	$59.8842	$59.88	$59.90	$59.90
Purchase #7	$143.85	6.716%	$153.511	$153.51	$153.50	$153.50
7 purchase totals =	$553.87		$589.2720	$589.27	$589.30	$589.30