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	$244.39	10.573%	$270.2294	$270.23	$270.25	$270.20
Purchase #2	$92.72	11.732%	$103.5979	$103.60	$103.60	$103.60
Purchase #3	$196.71	4.408%	$205.381	$205.38	$205.40	$205.40
Purchase #4	$72.43	11.690%	$80.8971	$80.90	$80.90	$80.90
Purchase #5	$247.27	12.695%	$278.6609	$278.66	$278.65	$278.70
Purchase #6	$167.63	4.103%	$174.5079	$174.51	$174.50	$174.50
Purchase #7	$57.40	5.844%	$60.7545	$60.75	$60.75	$60.80
7 purchase totals =	$1,078.55		$1,174.0287	$1,174.03	$1,174.05	$1,174.10