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	$114.95	5.435%	$121.1975	$121.20	$121.20	$121.20
Purchase #2	$42.56	5.151%	$44.7523	$44.75	$44.75	$44.80
Purchase #3	$107.71	5.734%	$113.8861	$113.89	$113.90	$113.90
Purchase #4	$78.88	3.445%	$81.5974	$81.60	$81.60	$81.60
Purchase #5	$95.72	4.255%	$99.7929	$99.79	$99.80	$99.80
Purchase #6	$99.75	9.673%	$109.3988	$109.40	$109.40	$109.40
Purchase #7	$155.91	7.494%	$167.5939	$167.59	$167.60	$167.60
7 purchase totals =	$695.48		$738.2189	$738.22	$738.25	$738.30