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	$178.42	4.140%	$185.8066	$185.81	$185.80	$185.80
Purchase #2	$43.90	11.864%	$49.1083	$49.11	$49.10	$49.10
Purchase #3	$49.75	11.539%	$55.4907	$55.49	$55.50	$55.50
Purchase #4	$39.90	9.268%	$43.5979	$43.60	$43.60	$43.60
Purchase #5	$99.63	3.122%	$102.7404	$102.74	$102.75	$102.70
Purchase #6	$82.71	13.296%	$93.7071	$93.71	$93.70	$93.70
Purchase #7	$169.46	3.158%	$174.8115	$174.81	$174.80	$174.80
7 purchase totals =	$663.77		$705.2625	$705.27	$705.25	$705.20