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	$171.82	9.475%	$188.0999	$188.10	$188.10	$188.10
Purchase #2	$64.55	4.583%	$67.5083	$67.51	$67.50	$67.50
Purchase #3	$181.56	7.448%	$195.0826	$195.08	$195.10	$195.10
Purchase #4	$225.83	3.743%	$234.2828	$234.28	$234.30	$234.30
Purchase #5	$174.28	12.830%	$196.6401	$196.64	$196.65	$196.60
Purchase #6	$43.82	3.760%	$45.4676	$45.47	$45.45	$45.50
Purchase #7	$109.78	8.317%	$118.9104	$118.91	$118.90	$118.90
7 purchase totals =	$971.64		$1,045.9917	$1,045.99	$1,046.00	$1,046.00