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	$105.65	3.127%	$108.9537	$108.95	$108.95	$109.00
Purchase #2	$67.32	4.416%	$70.2929	$70.29	$70.30	$70.30
Purchase #3	$145.59	11.190%	$161.8815	$161.88	$161.90	$161.90
Purchase #4	$195.28	7.146%	$209.2347	$209.23	$209.25	$209.20
Purchase #5	$145.49	11.757%	$162.5953	$162.60	$162.60	$162.60
Purchase #6	$183.59	11.390%	$204.5009	$204.50	$204.50	$204.50
Purchase #7	$176.57	6.400%	$187.8705	$187.87	$187.85	$187.90
7 purchase totals =	$1,019.49		$1,105.3295	$1,105.32	$1,105.35	$1,105.40