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	$65.83	9.276%	$71.9364	$71.94	$71.95	$71.90
Purchase #2	$88.93	9.451%	$97.3348	$97.33	$97.35	$97.30
Purchase #3	$91.34	11.214%	$101.5829	$101.58	$101.60	$101.60
Purchase #4	$20.58	11.789%	$23.0062	$23.01	$23.00	$23.00
Purchase #5	$52.58	3.773%	$54.5638	$54.56	$54.55	$54.60
Purchase #6	$56.75	7.591%	$61.0579	$61.06	$61.05	$61.10
Purchase #7	$159.33	4.773%	$166.9348	$166.93	$166.95	$166.90
7 purchase totals =	$535.34		$576.4168	$576.41	$576.45	$576.40