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	$94.40	11.552%	$105.3051	$105.31	$105.30	$105.30
Purchase #2	$70.36	13.861%	$80.1126	$80.11	$80.10	$80.10
Purchase #3	$107.41	6.544%	$114.4389	$114.44	$114.45	$114.40
Purchase #4	$184.94	3.604%	$191.6052	$191.61	$191.60	$191.60
Purchase #5	$131.33	3.824%	$136.3521	$136.35	$136.35	$136.40
Purchase #6	$63.72	13.601%	$72.3866	$72.39	$72.40	$72.40
Purchase #7	$185.27	9.705%	$203.2505	$203.25	$203.25	$203.30
7 purchase totals =	$837.43		$903.4510	$903.46	$903.45	$903.50