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	$43.40	7.522%	$46.6645	$46.66	$46.65	$46.70
Purchase #2	$96.50	3.446%	$99.8254	$99.83	$99.85	$99.80
Purchase #3	$36.27	13.435%	$41.1429	$41.14	$41.15	$41.10
Purchase #4	$67.68	5.309%	$71.2731	$71.27	$71.25	$71.30
Purchase #5	$233.42	11.650%	$260.6134	$260.61	$260.60	$260.60
Purchase #6	$142.90	13.651%	$162.4073	$162.41	$162.40	$162.40
Purchase #7	$101.84	7.395%	$109.3711	$109.37	$109.35	$109.40
7 purchase totals =	$722.01		$791.2977	$791.29	$791.25	$791.30