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	$118.71	10.818%	$131.552	$131.55	$131.55	$131.60
Purchase #2	$227.27	10.266%	$250.6015	$250.60	$250.60	$250.60
Purchase #3	$38.73	3.436%	$40.0608	$40.06	$40.05	$40.10
Purchase #4	$191.98	7.251%	$205.9005	$205.90	$205.90	$205.90
Purchase #5	$11.99	7.581%	$12.899	$12.90	$12.90	$12.90
Purchase #6	$99.97	11.789%	$111.7555	$111.76	$111.75	$111.80
Purchase #7	$171.88	7.178%	$184.2175	$184.22	$184.20	$184.20
7 purchase totals =	$860.53		$936.9868	$936.99	$936.95	$937.10