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	$196.38	5.734%	$207.6404	$207.64	$207.65	$207.60
Purchase #2	$124.37	12.469%	$139.8777	$139.88	$139.90	$139.90
Purchase #3	$27.97	3.380%	$28.9154	$28.92	$28.90	$28.90
Purchase #4	$80.27	10.480%	$88.6823	$88.68	$88.70	$88.70
Purchase #5	$154.67	6.355%	$164.4993	$164.50	$164.50	$164.50
Purchase #6	$97.57	11.392%	$108.6852	$108.69	$108.70	$108.70
Purchase #7	$39.50	10.152%	$43.51	$43.51	$43.50	$43.50
7 purchase totals =	$720.73		$781.8103	$781.82	$781.85	$781.80