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	$152.78	13.269%	$173.0524	$173.05	$173.05	$173.10
Purchase #2	$86.33	13.560%	$98.0363	$98.04	$98.05	$98.00
Purchase #3	$153.49	7.308%	$164.707	$164.71	$164.70	$164.70
Purchase #4	$81.99	10.405%	$90.5211	$90.52	$90.50	$90.50
Purchase #5	$138.81	12.514%	$156.1807	$156.18	$156.20	$156.20
Purchase #6	$95.70	6.696%	$102.1081	$102.11	$102.10	$102.10
Purchase #7	$175.83	4.801%	$184.2716	$184.27	$184.25	$184.30
7 purchase totals =	$884.93		$968.8772	$968.88	$968.85	$968.90