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	$82.76	4.369%	$86.3758	$86.38	$86.40	$86.40
Purchase #2	$183.64	8.576%	$199.389	$199.39	$199.40	$199.40
Purchase #3	$87.29	5.657%	$92.228	$92.23	$92.25	$92.20
Purchase #4	$73.85	5.864%	$78.1806	$78.18	$78.20	$78.20
Purchase #5	$11.50	13.871%	$13.0952	$13.10	$13.10	$13.10
Purchase #6	$188.74	12.592%	$212.5061	$212.51	$212.50	$212.50
Purchase #7	$233.45	11.498%	$260.2921	$260.29	$260.30	$260.30
7 purchase totals =	$861.23		$942.0668	$942.08	$942.15	$942.10