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	$125.93	8.726%	$136.9187	$136.92	$136.90	$136.90
Purchase #2	$43.83	4.764%	$45.9181	$45.92	$45.90	$45.90
Purchase #3	$51.96	3.361%	$53.7064	$53.71	$53.70	$53.70
Purchase #4	$78.32	12.628%	$88.2102	$88.21	$88.20	$88.20
Purchase #5	$77.80	5.634%	$82.1833	$82.18	$82.20	$82.20
Purchase #6	$125.86	10.521%	$139.1017	$139.10	$139.10	$139.10
Purchase #7	$178.36	12.164%	$200.0557	$200.06	$200.05	$200.10
7 purchase totals =	$682.06		$746.0941	$746.10	$746.05	$746.10