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	$148.49	9.432%	$162.4956	$162.50	$162.50	$162.50
Purchase #2	$90.87	9.179%	$99.211	$99.21	$99.20	$99.20
Purchase #3	$83.66	5.626%	$88.3667	$88.37	$88.35	$88.40
Purchase #4	$105.31	6.564%	$112.2225	$112.22	$112.20	$112.20
Purchase #5	$13.95	9.739%	$15.3086	$15.31	$15.30	$15.30
Purchase #6	$50.76	3.402%	$52.4869	$52.49	$52.50	$52.50
Purchase #7	$179.55	7.407%	$192.8493	$192.85	$192.85	$192.80
7 purchase totals =	$672.59		$722.9406	$722.95	$722.90	$722.90