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	$182.27	3.105%	$187.9295	$187.93	$187.95	$187.90
Purchase #2	$102.89	10.858%	$114.0618	$114.06	$114.05	$114.10
Purchase #3	$67.50	3.799%	$70.0643	$70.06	$70.05	$70.10
Purchase #4	$118.85	5.263%	$125.1051	$125.11	$125.10	$125.10
Purchase #5	$241.87	10.580%	$267.4598	$267.46	$267.45	$267.50
Purchase #6	$198.32	13.622%	$225.3352	$225.34	$225.35	$225.30
Purchase #7	$73.89	11.336%	$82.2662	$82.27	$82.25	$82.30
7 purchase totals =	$985.59		$1,072.2219	$1,072.23	$1,072.20	$1,072.30