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	$55.94	7.137%	$59.9324	$59.93	$59.95	$59.90
Purchase #2	$216.52	7.791%	$233.3891	$233.39	$233.40	$233.40
Purchase #3	$111.39	3.712%	$115.5248	$115.52	$115.50	$115.50
Purchase #4	$84.51	5.791%	$89.404	$89.40	$89.40	$89.40
Purchase #5	$55.65	5.583%	$58.7569	$58.76	$58.75	$58.80
Purchase #6	$212.95	6.552%	$226.9025	$226.90	$226.90	$226.90
Purchase #7	$189.37	5.600%	$199.9747	$199.97	$199.95	$200.00
7 purchase totals =	$926.33		$983.8844	$983.87	$983.85	$983.90