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	$101.29	7.722%	$109.1116	$109.11	$109.10	$109.10
Purchase #2	$194.97	3.328%	$201.4586	$201.46	$201.45	$201.50
Purchase #3	$23.82	6.190%	$25.2945	$25.29	$25.30	$25.30
Purchase #4	$122.31	13.753%	$139.1313	$139.13	$139.15	$139.10
Purchase #5	$249.77	5.807%	$264.2741	$264.27	$264.25	$264.30
Purchase #6	$107.90	11.696%	$120.52	$120.52	$120.50	$120.50
Purchase #7	$164.38	9.371%	$179.784	$179.78	$179.80	$179.80
7 purchase totals =	$964.44		$1,039.5741	$1,039.56	$1,039.55	$1,039.60