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	$119.30	10.567%	$131.9064	$131.91	$131.90	$131.90
Purchase #2	$243.33	11.281%	$270.7801	$270.78	$270.80	$270.80
Purchase #3	$214.97	6.470%	$228.8786	$228.88	$228.90	$228.90
Purchase #4	$19.47	6.226%	$20.6822	$20.68	$20.70	$20.70
Purchase #5	$28.98	8.659%	$31.4894	$31.49	$31.50	$31.50
Purchase #6	$209.86	12.311%	$235.6959	$235.70	$235.70	$235.70
Purchase #7	$180.50	6.209%	$191.7072	$191.71	$191.70	$191.70
7 purchase totals =	$1,016.41		$1,111.1398	$1,111.15	$1,111.20	$1,111.20