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	$114.40	7.761%	$123.2786	$123.28	$123.30	$123.30
Purchase #2	$87.37	4.439%	$91.2484	$91.25	$91.25	$91.20
Purchase #3	$177.89	3.326%	$183.8066	$183.81	$183.80	$183.80
Purchase #4	$243.52	8.771%	$264.8791	$264.88	$264.90	$264.90
Purchase #5	$166.88	7.526%	$179.4394	$179.44	$179.45	$179.40
Purchase #6	$170.47	7.417%	$183.1138	$183.11	$183.10	$183.10
Purchase #7	$109.88	7.426%	$118.0397	$118.04	$118.05	$118.00
7 purchase totals =	$1,070.41		$1,143.8056	$1,143.81	$1,143.85	$1,143.70