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	$175.25	5.237%	$184.4278	$184.43	$184.45	$184.40
Purchase #2	$67.88	9.582%	$74.3843	$74.38	$74.40	$74.40
Purchase #3	$127.43	3.506%	$131.8977	$131.90	$131.90	$131.90
Purchase #4	$197.31	5.813%	$208.7796	$208.78	$208.80	$208.80
Purchase #5	$124.87	4.304%	$130.2444	$130.24	$130.25	$130.20
Purchase #6	$116.37	3.790%	$120.7804	$120.78	$120.80	$120.80
Purchase #7	$174.46	8.505%	$189.2978	$189.30	$189.30	$189.30
7 purchase totals =	$983.57		$1,039.8120	$1,039.81	$1,039.90	$1,039.80