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	$127.98	11.329%	$142.4789	$142.48	$142.50	$142.50
Purchase #2	$6.89	10.540%	$7.6162	$7.62	$7.60	$7.60
Purchase #3	$55.64	12.182%	$62.4181	$62.42	$62.40	$62.40
Purchase #4	$6.75	12.332%	$7.5824	$7.58	$7.60	$7.60
Purchase #5	$171.91	10.424%	$189.8299	$189.83	$189.85	$189.80
Purchase #6	$132.88	8.688%	$144.4246	$144.42	$144.40	$144.40
Purchase #7	$135.25	12.617%	$152.3145	$152.31	$152.30	$152.30
7 purchase totals =	$637.30		$706.6646	$706.66	$706.65	$706.60