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	$23.29	3.509%	$24.1072	$24.11	$24.10	$24.10
Purchase #2	$174.28	9.793%	$191.3472	$191.35	$191.35	$191.30
Purchase #3	$102.86	8.403%	$111.5033	$111.50	$111.50	$111.50
Purchase #4	$43.35	5.507%	$45.7373	$45.74	$45.75	$45.70
Purchase #5	$203.43	12.681%	$229.227	$229.23	$229.25	$229.20
Purchase #6	$147.93	11.203%	$164.5026	$164.50	$164.50	$164.50
Purchase #7	$241.64	11.258%	$268.8438	$268.84	$268.85	$268.80
7 purchase totals =	$936.78		$1,035.2684	$1,035.27	$1,035.30	$1,035.10