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	$204.63	12.372%	$229.9468	$229.95	$229.95	$229.90
Purchase #2	$30.90	4.260%	$32.2163	$32.22	$32.20	$32.20
Purchase #3	$208.33	8.222%	$225.4589	$225.46	$225.45	$225.50
Purchase #4	$196.71	9.801%	$215.9895	$215.99	$216.00	$216.00
Purchase #5	$109.41	13.790%	$124.4976	$124.50	$124.50	$124.50
Purchase #6	$243.46	6.149%	$258.4304	$258.43	$258.45	$258.40
Purchase #7	$53.99	10.269%	$59.5342	$59.53	$59.55	$59.50
7 purchase totals =	$1,047.43		$1,146.0737	$1,146.08	$1,146.10	$1,146.00