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	$46.87	12.113%	$52.5474	$52.55	$52.55	$52.50
Purchase #2	$19.63	9.788%	$21.5514	$21.55	$21.55	$21.60
Purchase #3	$90.34	12.523%	$101.6533	$101.65	$101.65	$101.70
Purchase #4	$156.76	3.718%	$162.5883	$162.59	$162.60	$162.60
Purchase #5	$120.58	6.456%	$128.3646	$128.36	$128.35	$128.40
Purchase #6	$128.50	9.648%	$140.8977	$140.90	$140.90	$140.90
Purchase #7	$86.86	10.664%	$96.1228	$96.12	$96.10	$96.10
7 purchase totals =	$649.54		$703.7255	$703.72	$703.70	$703.80