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	$148.46	5.419%	$156.505	$156.51	$156.50	$156.50
Purchase #2	$86.65	11.518%	$96.6303	$96.63	$96.65	$96.60
Purchase #3	$48.78	3.410%	$50.4434	$50.44	$50.45	$50.40
Purchase #4	$13.63	9.464%	$14.9199	$14.92	$14.90	$14.90
Purchase #5	$192.62	12.818%	$217.31	$217.31	$217.30	$217.30
Purchase #6	$52.48	13.804%	$59.7243	$59.72	$59.70	$59.70
Purchase #7	$94.52	10.715%	$104.6478	$104.65	$104.65	$104.60
7 purchase totals =	$637.14		$700.1807	$700.18	$700.15	$700.00