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	$75.32	10.150%	$82.965	$82.97	$82.95	$83.00
Purchase #2	$25.78	12.516%	$29.0066	$29.01	$29.00	$29.00
Purchase #3	$134.26	12.163%	$150.59	$150.59	$150.60	$150.60
Purchase #4	$183.34	7.338%	$196.7935	$196.79	$196.80	$196.80
Purchase #5	$112.44	10.541%	$124.2923	$124.29	$124.30	$124.30
Purchase #6	$53.83	11.291%	$59.9079	$59.91	$59.90	$59.90
Purchase #7	$41.32	11.558%	$46.0958	$46.10	$46.10	$46.10
7 purchase totals =	$626.29		$689.6511	$689.66	$689.65	$689.70