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	$156.88	10.755%	$173.7524	$173.75	$173.75	$173.80
Purchase #2	$192.90	8.258%	$208.8297	$208.83	$208.85	$208.80
Purchase #3	$55.28	7.551%	$59.4542	$59.45	$59.45	$59.50
Purchase #4	$208.93	6.217%	$221.9192	$221.92	$221.90	$221.90
Purchase #5	$106.78	5.771%	$112.9423	$112.94	$112.95	$112.90
Purchase #6	$85.35	4.789%	$89.4374	$89.44	$89.45	$89.40
Purchase #7	$74.67	6.179%	$79.2839	$79.28	$79.30	$79.30
7 purchase totals =	$880.79		$945.6191	$945.61	$945.65	$945.60