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	$233.71	8.661%	$253.9516	$253.95	$253.95	$254.00
Purchase #2	$36.61	4.463%	$38.2439	$38.24	$38.25	$38.20
Purchase #3	$174.72	12.496%	$196.553	$196.55	$196.55	$196.60
Purchase #4	$47.92	11.238%	$53.3052	$53.31	$53.30	$53.30
Purchase #5	$72.61	3.404%	$75.0816	$75.08	$75.10	$75.10
Purchase #6	$112.46	9.374%	$123.002	$123.00	$123.00	$123.00
Purchase #7	$126.75	3.385%	$131.0405	$131.04	$131.05	$131.00
7 purchase totals =	$804.78		$871.1778	$871.17	$871.20	$871.20