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	$207.59	4.116%	$216.1344	$216.13	$216.15	$216.10
Purchase #2	$46.36	12.417%	$52.1165	$52.12	$52.10	$52.10
Purchase #3	$75.32	4.174%	$78.4639	$78.46	$78.45	$78.50
Purchase #4	$105.51	12.328%	$118.5173	$118.52	$118.50	$118.50
Purchase #5	$168.85	12.454%	$189.8786	$189.88	$189.90	$189.90
Purchase #6	$66.48	9.649%	$72.8947	$72.89	$72.90	$72.90
Purchase #7	$118.95	4.234%	$123.9863	$123.99	$124.00	$124.00
7 purchase totals =	$789.06		$851.9917	$851.99	$852.00	$852.00