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	$205.93	13.755%	$234.2557	$234.26	$234.25	$234.30
Purchase #2	$246.81	11.765%	$275.8472	$275.85	$275.85	$275.80
Purchase #3	$89.51	3.459%	$92.6062	$92.61	$92.60	$92.60
Purchase #4	$47.82	3.290%	$49.3933	$49.39	$49.40	$49.40
Purchase #5	$154.26	9.456%	$168.8468	$168.85	$168.85	$168.80
Purchase #6	$233.38	4.578%	$244.0641	$244.06	$244.05	$244.10
Purchase #7	$89.81	13.237%	$101.6981	$101.70	$101.70	$101.70
7 purchase totals =	$1,067.52		$1,166.7114	$1,166.72	$1,166.70	$1,166.70