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	$32.97	5.752%	$34.8664	$34.87	$34.85	$34.90
Purchase #2	$248.31	8.269%	$268.8428	$268.84	$268.85	$268.80
Purchase #3	$135.66	6.374%	$144.307	$144.31	$144.30	$144.30
Purchase #4	$219.48	8.853%	$238.9106	$238.91	$238.90	$238.90
Purchase #5	$42.42	8.746%	$46.1301	$46.13	$46.15	$46.10
Purchase #6	$153.73	12.594%	$173.0908	$173.09	$173.10	$173.10
Purchase #7	$79.47	13.655%	$90.3216	$90.32	$90.30	$90.30
7 purchase totals =	$912.04		$996.4693	$996.47	$996.45	$996.40