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	$173.86	10.257%	$191.6928	$191.69	$191.70	$191.70
Purchase #2	$246.64	10.801%	$273.2796	$273.28	$273.30	$273.30
Purchase #3	$82.80	3.362%	$85.5837	$85.58	$85.60	$85.60
Purchase #4	$36.29	5.613%	$38.327	$38.33	$38.35	$38.30
Purchase #5	$234.80	10.527%	$259.5174	$259.52	$259.50	$259.50
Purchase #6	$7.59	3.689%	$7.87	$7.87	$7.85	$7.90
Purchase #7	$220.78	9.719%	$242.2376	$242.24	$242.25	$242.20
7 purchase totals =	$1,002.76		$1,098.5081	$1,098.51	$1,098.55	$1,098.50