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	$6.88	12.573%	$7.745	$7.75	$7.75	$7.70
Purchase #2	$40.90	11.335%	$45.536	$45.54	$45.55	$45.50
Purchase #3	$112.48	4.577%	$117.6282	$117.63	$117.65	$117.60
Purchase #4	$93.37	10.279%	$102.9675	$102.97	$102.95	$103.00
Purchase #5	$99.72	4.725%	$104.4318	$104.43	$104.45	$104.40
Purchase #6	$49.37	4.314%	$51.4998	$51.50	$51.50	$51.50
Purchase #7	$41.50	11.425%	$46.2414	$46.24	$46.25	$46.20
7 purchase totals =	$444.22		$476.0497	$476.06	$476.10	$475.90