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	$233.68	6.549%	$248.9837	$248.98	$249.00	$249.00
Purchase #2	$233.75	4.456%	$244.1659	$244.17	$244.15	$244.20
Purchase #3	$43.63	4.341%	$45.524	$45.52	$45.50	$45.50
Purchase #4	$220.44	10.429%	$243.4297	$243.43	$243.45	$243.40
Purchase #5	$78.34	5.165%	$82.3863	$82.39	$82.40	$82.40
Purchase #6	$46.31	9.599%	$50.7553	$50.76	$50.75	$50.80
Purchase #7	$84.46	5.271%	$88.9119	$88.91	$88.90	$88.90
7 purchase totals =	$940.61		$1,004.1568	$1,004.16	$1,004.15	$1,004.20