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	$41.69	9.378%	$45.5997	$45.60	$45.60	$45.60
Purchase #2	$76.49	13.451%	$86.7787	$86.78	$86.80	$86.80
Purchase #3	$82.56	12.348%	$92.7545	$92.75	$92.75	$92.80
Purchase #4	$230.81	4.384%	$240.9287	$240.93	$240.95	$240.90
Purchase #5	$85.26	13.254%	$96.5604	$96.56	$96.55	$96.60
Purchase #6	$150.42	12.127%	$168.6614	$168.66	$168.65	$168.70
Purchase #7	$187.97	4.675%	$196.7576	$196.76	$196.75	$196.80
7 purchase totals =	$855.20		$928.0410	$928.04	$928.05	$928.20