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	$120.54	5.290%	$126.9166	$126.92	$126.90	$126.90
Purchase #2	$100.87	10.757%	$111.7206	$111.72	$111.70	$111.70
Purchase #3	$58.75	4.380%	$61.3233	$61.32	$61.30	$61.30
Purchase #4	$40.27	6.226%	$42.7772	$42.78	$42.80	$42.80
Purchase #5	$31.80	10.435%	$35.1183	$35.12	$35.10	$35.10
Purchase #6	$196.77	8.818%	$214.1212	$214.12	$214.10	$214.10
Purchase #7	$223.37	4.210%	$232.7739	$232.77	$232.75	$232.80
7 purchase totals =	$772.37		$824.7511	$824.75	$824.65	$824.70