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	$172.25	5.615%	$181.9218	$181.92	$181.90	$181.90
Purchase #2	$171.41	9.592%	$187.8516	$187.85	$187.85	$187.90
Purchase #3	$18.29	10.532%	$20.2163	$20.22	$20.20	$20.20
Purchase #4	$230.52	10.793%	$255.4	$255.40	$255.40	$255.40
Purchase #5	$27.48	10.860%	$30.4643	$30.46	$30.45	$30.50
Purchase #6	$241.63	12.512%	$271.8627	$271.86	$271.85	$271.90
Purchase #7	$78.26	5.459%	$82.5322	$82.53	$82.55	$82.50
7 purchase totals =	$939.84		$1,030.2489	$1,030.24	$1,030.20	$1,030.30