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	$248.59	10.827%	$275.5048	$275.50	$275.50	$275.50
Purchase #2	$96.93	6.285%	$103.0221	$103.02	$103.00	$103.00
Purchase #3	$181.46	8.416%	$196.7317	$196.73	$196.75	$196.70
Purchase #4	$129.76	13.622%	$147.4359	$147.44	$147.45	$147.40
Purchase #5	$171.49	11.412%	$191.0604	$191.06	$191.05	$191.10
Purchase #6	$30.32	11.510%	$33.8098	$33.81	$33.80	$33.80
Purchase #7	$152.72	3.146%	$157.5246	$157.52	$157.50	$157.50
7 purchase totals =	$1,011.27		$1,105.0893	$1,105.08	$1,105.05	$1,105.00