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	$164.56	13.813%	$187.2907	$187.29	$187.30	$187.30
Purchase #2	$237.28	7.237%	$254.452	$254.45	$254.45	$254.50
Purchase #3	$156.26	12.168%	$175.2737	$175.27	$175.25	$175.30
Purchase #4	$69.43	4.469%	$72.5328	$72.53	$72.55	$72.50
Purchase #5	$90.96	5.613%	$96.0656	$96.07	$96.05	$96.10
Purchase #6	$25.26	10.118%	$27.8158	$27.82	$27.80	$27.80
Purchase #7	$238.81	12.568%	$268.8236	$268.82	$268.80	$268.80
7 purchase totals =	$982.56		$1,082.2542	$1,082.25	$1,082.20	$1,082.30