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	$138.68	12.434%	$155.9235	$155.92	$155.90	$155.90
Purchase #2	$8.40	6.166%	$8.9179	$8.92	$8.90	$8.90
Purchase #3	$136.31	4.680%	$142.6893	$142.69	$142.70	$142.70
Purchase #4	$47.69	11.715%	$53.2769	$53.28	$53.30	$53.30
Purchase #5	$221.77	3.138%	$228.7291	$228.73	$228.75	$228.70
Purchase #6	$92.99	7.438%	$99.9066	$99.91	$99.90	$99.90
Purchase #7	$66.57	6.437%	$70.8551	$70.86	$70.85	$70.90
7 purchase totals =	$712.41		$760.2984	$760.31	$760.30	$760.30