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	$51.60	4.292%	$53.8147	$53.81	$53.80	$53.80
Purchase #2	$86.78	8.287%	$93.9715	$93.97	$93.95	$94.00
Purchase #3	$94.43	6.170%	$100.2563	$100.26	$100.25	$100.30
Purchase #4	$51.61	6.180%	$54.7995	$54.80	$54.80	$54.80
Purchase #5	$111.39	11.120%	$123.7766	$123.78	$123.80	$123.80
Purchase #6	$39.52	6.216%	$41.9766	$41.98	$42.00	$42.00
Purchase #7	$165.81	13.869%	$188.8062	$188.81	$188.80	$188.80
7 purchase totals =	$601.14		$657.4014	$657.41	$657.40	$657.50