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	$242.87	11.134%	$269.9111	$269.91	$269.90	$269.90
Purchase #2	$170.66	9.862%	$187.4905	$187.49	$187.50	$187.50
Purchase #3	$149.37	11.867%	$167.0957	$167.10	$167.10	$167.10
Purchase #4	$95.83	13.503%	$108.7699	$108.77	$108.75	$108.80
Purchase #5	$59.78	5.176%	$62.8742	$62.87	$62.85	$62.90
Purchase #6	$101.82	9.288%	$111.277	$111.28	$111.30	$111.30
Purchase #7	$125.33	11.589%	$139.8545	$139.85	$139.85	$139.90
7 purchase totals =	$945.66		$1,047.2729	$1,047.27	$1,047.25	$1,047.40