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	$43.30	10.282%	$47.7521	$47.75	$47.75	$47.80
Purchase #2	$243.51	11.421%	$271.3213	$271.32	$271.30	$271.30
Purchase #3	$103.50	7.399%	$111.158	$111.16	$111.15	$111.20
Purchase #4	$187.27	7.545%	$201.3995	$201.40	$201.40	$201.40
Purchase #5	$198.76	10.721%	$220.0691	$220.07	$220.05	$220.10
Purchase #6	$49.77	11.336%	$55.4119	$55.41	$55.40	$55.40
Purchase #7	$89.54	12.293%	$100.5472	$100.55	$100.55	$100.50
7 purchase totals =	$915.65		$1,007.6591	$1,007.66	$1,007.60	$1,007.70