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	$167.65	8.236%	$181.4577	$181.46	$181.45	$181.50
Purchase #2	$47.81	13.305%	$54.1711	$54.17	$54.15	$54.20
Purchase #3	$73.49	7.167%	$78.757	$78.76	$78.75	$78.80
Purchase #4	$167.76	4.407%	$175.1532	$175.15	$175.15	$175.20
Purchase #5	$136.59	11.828%	$152.7459	$152.75	$152.75	$152.70
Purchase #6	$237.79	10.273%	$262.2182	$262.22	$262.20	$262.20
Purchase #7	$19.53	5.804%	$20.6635	$20.66	$20.65	$20.70
7 purchase totals =	$850.62		$925.1666	$925.17	$925.10	$925.30