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	$111.27	13.524%	$126.3182	$126.32	$126.30	$126.30
Purchase #2	$7.47	3.815%	$7.755	$7.76	$7.75	$7.80
Purchase #3	$103.37	11.679%	$115.4426	$115.44	$115.45	$115.40
Purchase #4	$69.36	13.273%	$78.5662	$78.57	$78.55	$78.60
Purchase #5	$130.37	6.857%	$139.3095	$139.31	$139.30	$139.30
Purchase #6	$168.42	13.117%	$190.5117	$190.51	$190.50	$190.50
Purchase #7	$65.52	5.399%	$69.0574	$69.06	$69.05	$69.10
7 purchase totals =	$655.78		$726.9606	$726.97	$726.90	$727.00