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	$116.47	9.532%	$127.5719	$127.57	$127.55	$127.60
Purchase #2	$211.75	9.255%	$231.3475	$231.35	$231.35	$231.30
Purchase #3	$124.81	7.824%	$134.5751	$134.58	$134.60	$134.60
Purchase #4	$140.50	11.604%	$156.8036	$156.80	$156.80	$156.80
Purchase #5	$6.71	5.765%	$7.0968	$7.10	$7.10	$7.10
Purchase #6	$65.64	10.651%	$72.6313	$72.63	$72.65	$72.60
Purchase #7	$45.55	12.658%	$51.3157	$51.32	$51.30	$51.30
7 purchase totals =	$711.43		$781.3419	$781.35	$781.35	$781.30