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	$178.81	11.457%	$199.2963	$199.30	$199.30	$199.30
Purchase #2	$169.44	9.162%	$184.9641	$184.96	$184.95	$185.00
Purchase #3	$29.45	5.785%	$31.1537	$31.15	$31.15	$31.20
Purchase #4	$182.45	9.552%	$199.8776	$199.88	$199.90	$199.90
Purchase #5	$78.50	4.767%	$82.2421	$82.24	$82.25	$82.20
Purchase #6	$88.75	11.435%	$98.8986	$98.90	$98.90	$98.90
Purchase #7	$113.27	12.404%	$127.32	$127.32	$127.30	$127.30
7 purchase totals =	$840.67		$923.7524	$923.75	$923.75	$923.80