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	$171.40	13.514%	$194.563	$194.56	$194.55	$194.60
Purchase #2	$87.61	5.701%	$92.6046	$92.60	$92.60	$92.60
Purchase #3	$160.70	11.710%	$179.518	$179.52	$179.50	$179.50
Purchase #4	$84.54	6.198%	$89.7798	$89.78	$89.80	$89.80
Purchase #5	$102.61	9.765%	$112.6299	$112.63	$112.65	$112.60
Purchase #6	$247.95	10.167%	$273.1591	$273.16	$273.15	$273.20
Purchase #7	$123.97	11.773%	$138.565	$138.57	$138.55	$138.60
7 purchase totals =	$978.78		$1,080.8194	$1,080.82	$1,080.80	$1,080.90