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	$148.49	4.740%	$155.5284	$155.53	$155.55	$155.50
Purchase #2	$82.75	7.376%	$88.8536	$88.85	$88.85	$88.90
Purchase #3	$123.25	10.262%	$135.8979	$135.90	$135.90	$135.90
Purchase #4	$187.86	11.439%	$209.3493	$209.35	$209.35	$209.30
Purchase #5	$5.61	3.697%	$5.8174	$5.82	$5.80	$5.80
Purchase #6	$55.30	13.232%	$62.6173	$62.62	$62.60	$62.60
Purchase #7	$162.31	3.210%	$167.5202	$167.52	$167.50	$167.50
7 purchase totals =	$765.57		$825.5841	$825.59	$825.55	$825.50