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	$208.25	11.136%	$231.4407	$231.44	$231.45	$231.40
Purchase #2	$84.82	5.279%	$89.2976	$89.30	$89.30	$89.30
Purchase #3	$229.34	7.167%	$245.7768	$245.78	$245.80	$245.80
Purchase #4	$239.51	10.783%	$265.3364	$265.34	$265.35	$265.30
Purchase #5	$116.64	9.736%	$127.9961	$128.00	$128.00	$128.00
Purchase #6	$39.25	11.669%	$43.8301	$43.83	$43.85	$43.80
Purchase #7	$49.63	9.656%	$54.4223	$54.42	$54.40	$54.40
7 purchase totals =	$967.44		$1,058.1000	$1,058.11	$1,058.15	$1,058.00