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	$174.35	8.301%	$188.8228	$188.82	$188.80	$188.80
Purchase #2	$205.89	8.240%	$222.8553	$222.86	$222.85	$222.90
Purchase #3	$102.71	10.178%	$113.1638	$113.16	$113.15	$113.20
Purchase #4	$26.30	3.627%	$27.2539	$27.25	$27.25	$27.30
Purchase #5	$200.67	3.221%	$207.1336	$207.13	$207.15	$207.10
Purchase #6	$140.36	13.472%	$159.2693	$159.27	$159.25	$159.30
Purchase #7	$141.69	10.758%	$156.933	$156.93	$156.95	$156.90
7 purchase totals =	$991.97		$1,075.4317	$1,075.42	$1,075.40	$1,075.50