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	$218.82	10.430%	$241.6429	$241.64	$241.65	$241.60
Purchase #2	$67.63	7.304%	$72.5697	$72.57	$72.55	$72.60
Purchase #3	$38.41	8.326%	$41.608	$41.61	$41.60	$41.60
Purchase #4	$31.77	6.820%	$33.9367	$33.94	$33.95	$33.90
Purchase #5	$165.57	8.863%	$180.2445	$180.24	$180.25	$180.20
Purchase #6	$127.59	6.871%	$136.3567	$136.36	$136.35	$136.40
Purchase #7	$90.95	9.871%	$99.9277	$99.93	$99.95	$99.90
7 purchase totals =	$740.74		$806.2862	$806.29	$806.30	$806.20