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	$126.80	7.474%	$136.277	$136.28	$136.30	$136.30
Purchase #2	$48.64	13.551%	$55.2312	$55.23	$55.25	$55.20
Purchase #3	$226.52	9.641%	$248.3588	$248.36	$248.35	$248.40
Purchase #4	$195.40	10.269%	$215.4656	$215.47	$215.45	$215.50
Purchase #5	$51.90	4.463%	$54.2163	$54.22	$54.20	$54.20
Purchase #6	$152.39	9.124%	$166.2941	$166.29	$166.30	$166.30
Purchase #7	$225.88	3.545%	$233.8874	$233.89	$233.90	$233.90
7 purchase totals =	$1,027.53		$1,109.7304	$1,109.74	$1,109.75	$1,109.80