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	$121.37	7.753%	$130.7798	$130.78	$130.80	$130.80
Purchase #2	$19.33	6.297%	$20.5472	$20.55	$20.55	$20.50
Purchase #3	$50.70	5.404%	$53.4398	$53.44	$53.45	$53.40
Purchase #4	$123.31	5.741%	$130.3892	$130.39	$130.40	$130.40
Purchase #5	$24.83	10.411%	$27.4151	$27.42	$27.40	$27.40
Purchase #6	$180.93	3.839%	$187.8759	$187.88	$187.90	$187.90
Purchase #7	$165.38	4.140%	$172.2267	$172.23	$172.25	$172.20
7 purchase totals =	$685.85		$722.6737	$722.69	$722.75	$722.60