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	$222.72	5.307%	$234.5398	$234.54	$234.55	$234.50
Purchase #2	$25.69	12.591%	$28.9246	$28.92	$28.90	$28.90
Purchase #3	$137.85	7.714%	$148.4837	$148.48	$148.50	$148.50
Purchase #4	$134.73	13.673%	$153.1516	$153.15	$153.15	$153.20
Purchase #5	$153.52	10.675%	$169.9083	$169.91	$169.90	$169.90
Purchase #6	$29.83	5.599%	$31.5002	$31.50	$31.50	$31.50
Purchase #7	$79.76	8.669%	$86.6744	$86.67	$86.65	$86.70
7 purchase totals =	$784.10		$853.1826	$853.17	$853.15	$853.20