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	$92.54	5.809%	$97.9156	$97.92	$97.90	$97.90
Purchase #2	$100.78	3.742%	$104.5512	$104.55	$104.55	$104.60
Purchase #3	$123.42	12.152%	$138.418	$138.42	$138.40	$138.40
Purchase #4	$72.65	7.504%	$78.1017	$78.10	$78.10	$78.10
Purchase #5	$43.32	9.631%	$47.4921	$47.49	$47.50	$47.50
Purchase #6	$180.32	11.127%	$200.3842	$200.38	$200.40	$200.40
Purchase #7	$179.26	5.405%	$188.949	$188.95	$188.95	$188.90
7 purchase totals =	$792.29		$855.8118	$855.81	$855.80	$855.80