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	$115.40	6.728%	$123.1641	$123.16	$123.15	$123.20
Purchase #2	$218.84	7.756%	$235.8132	$235.81	$235.80	$235.80
Purchase #3	$152.56	12.798%	$172.0846	$172.08	$172.10	$172.10
Purchase #4	$231.30	12.167%	$259.4423	$259.44	$259.45	$259.40
Purchase #5	$62.99	6.527%	$67.1014	$67.10	$67.10	$67.10
Purchase #6	$18.27	10.663%	$20.2181	$20.22	$20.20	$20.20
Purchase #7	$167.32	8.433%	$181.4301	$181.43	$181.45	$181.40
7 purchase totals =	$966.68		$1,059.2538	$1,059.24	$1,059.25	$1,059.20