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	$250.96	8.481%	$272.2439	$272.24	$272.25	$272.20
Purchase #2	$43.64	5.361%	$45.9795	$45.98	$46.00	$46.00
Purchase #3	$124.92	7.757%	$134.61	$134.61	$134.60	$134.60
Purchase #4	$177.47	6.681%	$189.3268	$189.33	$189.35	$189.30
Purchase #5	$174.53	12.478%	$196.3079	$196.31	$196.30	$196.30
Purchase #6	$72.38	8.294%	$78.3832	$78.38	$78.40	$78.40
Purchase #7	$222.59	13.683%	$253.047	$253.05	$253.05	$253.00
7 purchase totals =	$1,066.49		$1,169.8983	$1,169.90	$1,169.95	$1,169.80