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	$162.41	13.496%	$184.3289	$184.33	$184.35	$184.30
Purchase #2	$42.79	8.525%	$46.4378	$46.44	$46.45	$46.40
Purchase #3	$84.97	3.859%	$88.249	$88.25	$88.25	$88.20
Purchase #4	$91.80	4.152%	$95.6115	$95.61	$95.60	$95.60
Purchase #5	$105.49	3.502%	$109.1843	$109.18	$109.20	$109.20
Purchase #6	$12.69	9.545%	$13.9013	$13.90	$13.90	$13.90
Purchase #7	$31.74	5.190%	$33.3873	$33.39	$33.40	$33.40
7 purchase totals =	$531.89		$571.1001	$571.10	$571.15	$571.00