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	$116.92	4.189%	$121.8178	$121.82	$121.80	$121.80
Purchase #2	$196.76	4.129%	$204.8842	$204.88	$204.90	$204.90
Purchase #3	$9.73	12.462%	$10.9426	$10.94	$10.95	$10.90
Purchase #4	$78.61	8.240%	$85.0875	$85.09	$85.10	$85.10
Purchase #5	$89.86	3.740%	$93.2208	$93.22	$93.20	$93.20
Purchase #6	$122.42	7.654%	$131.79	$131.79	$131.80	$131.80
Purchase #7	$110.54	7.285%	$118.5928	$118.59	$118.60	$118.60
7 purchase totals =	$724.84		$766.3357	$766.33	$766.35	$766.30