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	$143.31	9.860%	$157.4404	$157.44	$157.45	$157.40
Purchase #2	$147.68	6.270%	$156.9395	$156.94	$156.95	$156.90
Purchase #3	$65.38	10.774%	$72.424	$72.42	$72.40	$72.40
Purchase #4	$105.86	4.765%	$110.9042	$110.90	$110.90	$110.90
Purchase #5	$119.30	10.390%	$131.6953	$131.70	$131.70	$131.70
Purchase #6	$46.35	4.700%	$48.5285	$48.53	$48.55	$48.50
Purchase #7	$205.54	6.715%	$219.342	$219.34	$219.35	$219.30
7 purchase totals =	$833.42		$897.2739	$897.27	$897.30	$897.10