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	$211.69	7.345%	$227.2386	$227.24	$227.25	$227.20
Purchase #2	$165.39	9.192%	$180.5926	$180.59	$180.60	$180.60
Purchase #3	$226.90	10.872%	$251.5686	$251.57	$251.55	$251.60
Purchase #4	$240.67	7.551%	$258.843	$258.84	$258.85	$258.80
Purchase #5	$72.29	13.818%	$82.279	$82.28	$82.30	$82.30
Purchase #6	$123.63	10.254%	$136.307	$136.31	$136.30	$136.30
Purchase #7	$168.35	10.334%	$185.7473	$185.75	$185.75	$185.70
7 purchase totals =	$1,208.92		$1,322.5761	$1,322.58	$1,322.60	$1,322.50