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	$187.77	4.655%	$196.5107	$196.51	$196.50	$196.50
Purchase #2	$36.81	6.677%	$39.2678	$39.27	$39.25	$39.30
Purchase #3	$75.63	12.727%	$85.2554	$85.26	$85.25	$85.30
Purchase #4	$137.84	8.463%	$149.5054	$149.51	$149.50	$149.50
Purchase #5	$184.82	10.114%	$203.5127	$203.51	$203.50	$203.50
Purchase #6	$63.71	6.215%	$67.6696	$67.67	$67.65	$67.70
Purchase #7	$116.66	9.839%	$128.1382	$128.14	$128.15	$128.10
7 purchase totals =	$803.24		$869.8598	$869.87	$869.80	$869.90