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	$166.62	5.550%	$175.8674	$175.87	$175.85	$175.90
Purchase #2	$100.70	4.708%	$105.441	$105.44	$105.45	$105.40
Purchase #3	$82.73	5.763%	$87.4977	$87.50	$87.50	$87.50
Purchase #4	$68.83	4.465%	$71.9033	$71.90	$71.90	$71.90
Purchase #5	$88.77	4.622%	$92.8729	$92.87	$92.85	$92.90
Purchase #6	$162.79	6.499%	$173.3697	$173.37	$173.35	$173.40
Purchase #7	$209.33	6.490%	$222.9155	$222.92	$222.90	$222.90
7 purchase totals =	$879.77		$929.8675	$929.87	$929.80	$929.90