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	$227.47	6.541%	$242.3488	$242.35	$242.35	$242.30
Purchase #2	$74.32	3.688%	$77.0609	$77.06	$77.05	$77.10
Purchase #3	$136.98	9.735%	$150.315	$150.32	$150.30	$150.30
Purchase #4	$103.98	5.218%	$109.4057	$109.41	$109.40	$109.40
Purchase #5	$214.76	6.759%	$229.2756	$229.28	$229.30	$229.30
Purchase #6	$228.87	11.397%	$254.9543	$254.95	$254.95	$255.00
Purchase #7	$70.50	3.374%	$72.8787	$72.88	$72.90	$72.90
7 purchase totals =	$1,056.88		$1,136.2390	$1,136.25	$1,136.25	$1,136.30