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	$131.36	9.816%	$144.2543	$144.25	$144.25	$144.30
Purchase #2	$167.87	3.822%	$174.286	$174.29	$174.30	$174.30
Purchase #3	$63.97	13.147%	$72.3801	$72.38	$72.40	$72.40
Purchase #4	$105.66	12.429%	$118.7925	$118.79	$118.80	$118.80
Purchase #5	$166.75	10.607%	$184.4372	$184.44	$184.45	$184.40
Purchase #6	$27.79	3.414%	$28.7388	$28.74	$28.75	$28.70
Purchase #7	$152.52	9.570%	$167.1162	$167.12	$167.10	$167.10
7 purchase totals =	$815.92		$890.0051	$890.01	$890.05	$890.00