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	$128.81	3.833%	$133.7473	$133.75	$133.75	$133.70
Purchase #2	$203.88	9.152%	$222.5391	$222.54	$222.55	$222.50
Purchase #3	$69.48	6.388%	$73.9184	$73.92	$73.90	$73.90
Purchase #4	$166.69	12.342%	$187.2629	$187.26	$187.25	$187.30
Purchase #5	$33.87	4.718%	$35.468	$35.47	$35.45	$35.50
Purchase #6	$250.91	4.655%	$262.5899	$262.59	$262.60	$262.60
Purchase #7	$99.40	6.601%	$105.9614	$105.96	$105.95	$106.00
7 purchase totals =	$953.04		$1,021.4870	$1,021.49	$1,021.45	$1,021.50