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	$122.38	3.403%	$126.5446	$126.54	$126.55	$126.50
Purchase #2	$27.41	13.471%	$31.1024	$31.10	$31.10	$31.10
Purchase #3	$115.55	13.679%	$131.3561	$131.36	$131.35	$131.40
Purchase #4	$17.32	5.474%	$18.2681	$18.27	$18.25	$18.30
Purchase #5	$181.85	13.752%	$206.858	$206.86	$206.85	$206.90
Purchase #6	$169.75	13.861%	$193.279	$193.28	$193.30	$193.30
Purchase #7	$32.56	3.602%	$33.7328	$33.73	$33.75	$33.70
7 purchase totals =	$666.82		$741.1410	$741.14	$741.15	$741.20