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	$119.56	6.301%	$127.0935	$127.09	$127.10	$127.10
Purchase #2	$221.45	13.112%	$250.4865	$250.49	$250.50	$250.50
Purchase #3	$246.44	8.874%	$268.3091	$268.31	$268.30	$268.30
Purchase #4	$115.82	10.155%	$127.5815	$127.58	$127.60	$127.60
Purchase #5	$17.96	7.544%	$19.3149	$19.31	$19.30	$19.30
Purchase #6	$183.93	3.756%	$190.8384	$190.84	$190.85	$190.80
Purchase #7	$181.68	9.630%	$199.1758	$199.18	$199.20	$199.20
7 purchase totals =	$1,086.84		$1,182.7997	$1,182.80	$1,182.85	$1,182.80