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	$46.54	10.215%	$51.2941	$51.29	$51.30	$51.30
Purchase #2	$169.48	11.753%	$189.399	$189.40	$189.40	$189.40
Purchase #3	$210.60	11.847%	$235.5498	$235.55	$235.55	$235.50
Purchase #4	$168.83	9.407%	$184.7118	$184.71	$184.70	$184.70
Purchase #5	$43.61	11.341%	$48.5558	$48.56	$48.55	$48.60
Purchase #6	$174.82	5.294%	$184.075	$184.08	$184.10	$184.10
Purchase #7	$45.94	4.186%	$47.863	$47.86	$47.85	$47.90
7 purchase totals =	$859.82		$941.4485	$941.45	$941.45	$941.50