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	$127.71	3.160%	$131.7456	$131.75	$131.75	$131.70
Purchase #2	$30.63	12.184%	$34.362	$34.36	$34.35	$34.40
Purchase #3	$215.43	8.250%	$233.203	$233.20	$233.20	$233.20
Purchase #4	$212.33	6.862%	$226.9001	$226.90	$226.90	$226.90
Purchase #5	$48.33	11.330%	$53.8058	$53.81	$53.80	$53.80
Purchase #6	$238.60	11.337%	$265.6501	$265.65	$265.65	$265.70
Purchase #7	$129.91	8.717%	$141.2343	$141.23	$141.25	$141.20
7 purchase totals =	$1,002.94		$1,086.9009	$1,086.90	$1,086.90	$1,086.90