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	$33.68	5.724%	$35.6078	$35.61	$35.60	$35.60
Purchase #2	$43.38	4.440%	$45.3061	$45.31	$45.30	$45.30
Purchase #3	$50.26	8.406%	$54.4849	$54.48	$54.50	$54.50
Purchase #4	$234.98	5.281%	$247.3893	$247.39	$247.40	$247.40
Purchase #5	$79.32	3.808%	$82.3405	$82.34	$82.35	$82.30
Purchase #6	$197.75	13.612%	$224.6677	$224.67	$224.65	$224.70
Purchase #7	$161.52	8.317%	$174.9536	$174.95	$174.95	$175.00
7 purchase totals =	$800.89		$864.7499	$864.75	$864.75	$864.80