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	$220.97	11.450%	$246.2711	$246.27	$246.25	$246.30
Purchase #2	$100.92	9.374%	$110.3802	$110.38	$110.40	$110.40
Purchase #3	$148.44	11.520%	$165.5403	$165.54	$165.55	$165.50
Purchase #4	$226.85	3.545%	$234.8918	$234.89	$234.90	$234.90
Purchase #5	$179.27	6.824%	$191.5034	$191.50	$191.50	$191.50
Purchase #6	$167.74	5.142%	$176.3652	$176.37	$176.35	$176.40
Purchase #7	$44.97	6.436%	$47.8643	$47.86	$47.85	$47.90
7 purchase totals =	$1,089.16		$1,172.8163	$1,172.81	$1,172.80	$1,172.90