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	$67.89	4.657%	$71.0516	$71.05	$71.05	$71.10
Purchase #2	$132.95	8.415%	$144.1377	$144.14	$144.15	$144.10
Purchase #3	$71.51	9.732%	$78.4694	$78.47	$78.45	$78.50
Purchase #4	$52.54	6.668%	$56.0434	$56.04	$56.05	$56.00
Purchase #5	$220.78	8.440%	$239.4138	$239.41	$239.40	$239.40
Purchase #6	$218.94	13.646%	$248.8166	$248.82	$248.80	$248.80
Purchase #7	$147.65	13.622%	$167.7629	$167.76	$167.75	$167.80
7 purchase totals =	$912.26		$1,005.6954	$1,005.69	$1,005.65	$1,005.70