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	$35.38	6.424%	$37.6528	$37.65	$37.65	$37.70
Purchase #2	$29.39	5.205%	$30.9197	$30.92	$30.90	$30.90
Purchase #3	$11.82	10.200%	$13.0256	$13.03	$13.05	$13.00
Purchase #4	$50.82	9.177%	$55.4838	$55.48	$55.50	$55.50
Purchase #5	$136.42	11.490%	$152.0947	$152.09	$152.10	$152.10
Purchase #6	$46.61	5.224%	$49.0449	$49.04	$49.05	$49.00
Purchase #7	$183.48	7.188%	$196.6685	$196.67	$196.65	$196.70
7 purchase totals =	$493.92		$534.8900	$534.88	$534.90	$534.90