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	$124.50	5.579%	$131.4459	$131.45	$131.45	$131.40
Purchase #2	$175.46	3.826%	$182.1731	$182.17	$182.15	$182.20
Purchase #3	$110.53	6.281%	$117.4724	$117.47	$117.45	$117.50
Purchase #4	$232.49	12.368%	$261.2444	$261.24	$261.25	$261.20
Purchase #5	$191.83	4.165%	$199.8197	$199.82	$199.80	$199.80
Purchase #6	$38.46	10.815%	$42.6194	$42.62	$42.60	$42.60
Purchase #7	$215.33	10.198%	$237.2894	$237.29	$237.30	$237.30
7 purchase totals =	$1,088.60		$1,172.0643	$1,172.06	$1,172.00	$1,172.00