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	$71.34	3.487%	$73.8276	$73.83	$73.85	$73.80
Purchase #2	$235.33	11.135%	$261.534	$261.53	$261.55	$261.50
Purchase #3	$72.93	13.178%	$82.5407	$82.54	$82.55	$82.50
Purchase #4	$61.29	9.536%	$67.1346	$67.13	$67.15	$67.10
Purchase #5	$191.58	4.612%	$200.4157	$200.42	$200.40	$200.40
Purchase #6	$131.68	3.530%	$136.3283	$136.33	$136.35	$136.30
Purchase #7	$177.84	6.721%	$189.7926	$189.79	$189.80	$189.80
7 purchase totals =	$941.99		$1,011.5735	$1,011.57	$1,011.65	$1,011.40