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	$96.75	8.735%	$105.2011	$105.20	$105.20	$105.20
Purchase #2	$186.55	5.302%	$196.4409	$196.44	$196.45	$196.40
Purchase #3	$42.79	5.383%	$45.0934	$45.09	$45.10	$45.10
Purchase #4	$179.61	10.311%	$198.1296	$198.13	$198.15	$198.10
Purchase #5	$77.90	10.521%	$86.0959	$86.10	$86.10	$86.10
Purchase #6	$148.80	5.329%	$156.7296	$156.73	$156.75	$156.70
Purchase #7	$26.66	11.845%	$29.8179	$29.82	$29.80	$29.80
7 purchase totals =	$759.06		$817.5084	$817.51	$817.55	$817.40