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	$217.93	4.726%	$228.2294	$228.23	$228.25	$228.20
Purchase #2	$125.81	8.428%	$136.4133	$136.41	$136.40	$136.40
Purchase #3	$210.55	6.357%	$223.9347	$223.93	$223.95	$223.90
Purchase #4	$30.35	3.655%	$31.4593	$31.46	$31.45	$31.50
Purchase #5	$97.93	12.784%	$110.4494	$110.45	$110.45	$110.40
Purchase #6	$11.35	13.641%	$12.8983	$12.90	$12.90	$12.90
Purchase #7	$243.94	6.416%	$259.5912	$259.59	$259.60	$259.60
7 purchase totals =	$937.86		$1,002.9756	$1,002.97	$1,003.00	$1,002.90