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	$55.25	8.327%	$59.8507	$59.85	$59.85	$59.90
Purchase #2	$114.54	3.446%	$118.487	$118.49	$118.50	$118.50
Purchase #3	$94.93	3.762%	$98.5013	$98.50	$98.50	$98.50
Purchase #4	$164.43	13.550%	$186.7103	$186.71	$186.70	$186.70
Purchase #5	$229.55	10.651%	$253.9994	$254.00	$254.00	$254.00
Purchase #6	$99.33	11.833%	$111.0837	$111.08	$111.10	$111.10
Purchase #7	$103.66	8.780%	$112.7613	$112.76	$112.75	$112.80
7 purchase totals =	$861.69		$941.3937	$941.39	$941.40	$941.50