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	$119.53	5.328%	$125.8986	$125.90	$125.90	$125.90
Purchase #2	$242.52	10.749%	$268.5885	$268.59	$268.60	$268.60
Purchase #3	$101.91	9.227%	$111.3132	$111.31	$111.30	$111.30
Purchase #4	$195.35	11.494%	$217.8035	$217.80	$217.80	$217.80
Purchase #5	$104.70	7.278%	$112.3201	$112.32	$112.30	$112.30
Purchase #6	$61.82	5.851%	$65.4371	$65.44	$65.45	$65.40
Purchase #7	$138.97	9.619%	$152.3375	$152.34	$152.35	$152.30
7 purchase totals =	$964.80		$1,053.6985	$1,053.70	$1,053.70	$1,053.60