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	$40.82	4.174%	$42.5238	$42.52	$42.50	$42.50
Purchase #2	$46.54	4.255%	$48.5203	$48.52	$48.50	$48.50
Purchase #3	$163.27	12.747%	$184.082	$184.08	$184.10	$184.10
Purchase #4	$157.30	3.465%	$162.7504	$162.75	$162.75	$162.80
Purchase #5	$26.36	11.820%	$29.4758	$29.48	$29.50	$29.50
Purchase #6	$147.55	11.522%	$164.5507	$164.55	$164.55	$164.60
Purchase #7	$223.50	9.357%	$244.4129	$244.41	$244.40	$244.40
7 purchase totals =	$805.34		$876.3159	$876.31	$876.30	$876.40