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	$231.37	11.157%	$257.184	$257.18	$257.20	$257.20
Purchase #2	$78.39	13.611%	$89.0597	$89.06	$89.05	$89.10
Purchase #3	$64.66	11.306%	$71.9705	$71.97	$71.95	$72.00
Purchase #4	$96.43	7.874%	$104.0229	$104.02	$104.00	$104.00
Purchase #5	$76.32	13.419%	$86.5614	$86.56	$86.55	$86.60
Purchase #6	$234.39	11.115%	$260.4424	$260.44	$260.45	$260.40
Purchase #7	$200.91	10.632%	$222.2708	$222.27	$222.25	$222.30
7 purchase totals =	$982.47		$1,091.5117	$1,091.50	$1,091.45	$1,091.60